We're going to stick our necks out here and assume you've almost all got a mobile. Many can't cope without it. Yet millions are overpaying. Either by letting contracts roll over and effectively paying for a phone you already own, being hounded into expensive upgrades, or just not searching for the best deals.

So here's our challenge - cut your phone bill in half NOW. Full help in our 30+ Cheap Mobile Tips. Here are the key points...

1. Most shouldn't pay more than £10/mth. The cheapest way to run a phone is usually to own it outright (if you can) & pair with a top Sim. Data and call charges have massively dropped in recent years - that's why we say the key benchmark cost for most users is £10/mth (see point 2).

Start by estimating what allowances you need. Specialist free online tools such as Billmonitor* will log in to your online phone account and analyse your bills to find your cheapest tariff. MobilePhoneChecker* covers more networks. See Mobile matchmaking.

2. Check for the best Sim-only deals. They are increasingly popular due to their value and flexibility. You get a set amount of data, texts and calls for a fixed monthly price and they are usually cheapest.

- Best for low users: Get 1.5GB of data (4G), 250 mins and 5,000 texts for £5/mth on a 30-day rolling contract with Carphone-Warehouse-owned iD Mobile*, which uses the Three network.

- Best for medium users: We've blagged 5GB of data (4G), 1,500 mins and unltd texts for £10/mth with this 30-day rolling contract with BT-owned Plusnet Mobile*, for new and existing custs. It uses the EE network, and you've until next Tue to get it.

- Best for heavy users: Until Thu, this blagged 12mth contract from BT Mobile* gives a massive 20GB of data (4G), unltd mins and texts (on EE) for £16/mth if you've BT b'band, £21/mth if not. (To pay £16/mth click 'got BT b'band at home' in top right of page.) You also get a £100 Amzn or iTunes vch - annoyingly, BT WON'T remind you so you must claim the voucher within 2wks-3mths of sign-up.

For a full round-up of top deals, incl out-of-bundle costs; plus higher/lower use and other network deals, see Sim-only top picks.

3. New. Get £50 off the Samsung S8 or iPhone 7. These top-end handsets aren't MoneySaving... though if you'll get one anyway, do it as cheaply as possible. Discounts on newly launched handsets are rare, yet we've blagged £50 off the new Samsung S8 (released last Fri) AND the iPhone 7, from online retailer Unshackled.com*.

- £50 off code. Until Tue 9 May, use code MSE50 to take £50 off the upfront cost of either (when you click through, select 'outright'). This brings the Samsung S8* down to £639 and the 32GB iPhone 7* to £549, with next-day delivery included. (Unshackled says if you get the deal via a cashback site you won't get any cashback.)

- What if it runs out of stock? There's limited stock, particularly for the S8, so if it's right for you, go quick. Unshackled says it gets new deliveries every weekday and if it runs out you'll be invited to register and contacted within 24hrs of new stock arriving. The code will remain valid for a 'limited' time after.

- Will it be cheapest? Mobile prices change hourly, but these were the cheapest we could find from a UK-based retailer. You'll get a full UK manufacturer's warranty, so if something goes wrong you can take the handset to the nearest Samsung or Apple store (or authorised repair centre).

- But do you REALLY need a top-end smartphone? While many go wild for iPhones and Samsungs, there are plenty of low-cost models which search the web, play music, have cameras etc. See Cheap smartphone alternatives.

4. Save more by getting certified pre-owned handsets - our code gets a further £40 off the iPhone 6s, 6s Plus, 6 or 6 Plus. 'Certified pre-owned' iPhones are the gold standard of refurbs - refurbished by Apple to a very high standard (often they've never been used), but for a lower price. If you're happy to go with an older model, even just from last year, you can save big.

- Get £40 off many iPhones in the 6 & 6s range: Until Tue 9 May, use code MSE40 at Unshackled.com to get £40 off its 'certified pre-owned' iPhones (when you click through, select 'outright').

After the discount you'll pay £399 for a 16GB iPhone 6s*, £459 for a 16GB iPhone 6s Plus*, £559 for a 64GB iPhone 6s Plus*, £439 for a 64GB iPhone 6* or £409 for a 16GB iPhone 6 Plus*. They come with original box & accessories, 12mths' Apple warranty and next working day delivery. (Again, if you get the deal via a cashback site Unshacked says you won't get any cashback.)

See full info & other options in Refurbished Mobiles.

5. Can't afford to buy the phone upfront? Spread the cost INTEREST-FREE. While it's usually the cheapest way to buy, many balk at having to pay £100s upfront. Yet there are other ways to spread the cost which are usually much cheaper than a contract...

- Buy it upfront on a 0% spending credit card: This is a free way to spread the cost - you can currently get up to 30 interest-free months (see our 0% card best buys). ALWAYS make minimum repayments and clear it before the 0% ends.

- Interest-free iPhone 7 deal: Apple's running an ongoing deal to spread the cost of the iPhone 7 over 20 months - if you're approved. However, it's at full price - £50 more than our blagged deal above.

- Get a LOW interest rate with mobile financing: If you can't get approved for a 0% deal, specialist mobile finance providers loan you money for a handset at a cost - Unshackled is one, and our blagged codes work on its finance plans too. These usually beat most contracts, but ALWAYS do a comparison.

Cut your mobile phone bill in HALF
The cheapest way to run a phone is usually to own it outright (if you can) & pair with a top Sim

6. Sometimes contracts CAN win. As a rule, you'll pay more with a contract. Occasionally though contract re-sellers (middlemen between you and the network) can beat buying upfront and pairing with a Sim. See full help in our 14 Mobile Contract tips.

7. Going away? Roam free with a Three Sim. Using your phone abroad can be eye-wateringly expensive. Mercifully, from 15 Jun roaming fees in Europe will largely (though not entirely) disappear. Outside the EU it's a different story, with some providers charging up to £6/MB for data roaming.

Three's 'Feel At Home' lets you roam for free in 42 countries - incl some non-EU biggies such as the US & Australia. If you're not with Three you can still get the deal by picking up a free pay-as-you-go Sim. See our top-pick travel Sims in Cheap Mobile Roaming.

8. Contract up? Switch or haggle NOW. Mobile contracts have high monthly costs, yet once you reach your 'minimum term' the payments often continue - so you're effectively paying for a phone you already own.

Diarise to call your network 30 days before and give notice, then move to a Sim-only tariff - by switching to another deal or haggling down your bill with your existing provider, as Suzanne did: "My £24/mth phone contract was about to run out. Saw a good deal in the weekly email so went to EE armed with this info - it agreed to give me 5GB and unltd mins & texts for £8/mth. Thank you."

Mid-contract? You're likely stuck... The only way to escape is to pay the remainder of the contract in full (or thereabouts). If your provider hikes prices mid-contract you MAY be able to escape penalty-free - though they're allowed to raise tariffs by inflation each year.

9. Switching network's easy - and you can keep your number. Just request the PAC code from your current network to move your existing number over. The switch usually takes place the working day after you submit the PAC code to your new provider.

10. You're credit-checked if getting a contract. If your credit history is poor, PAYG may be your only option. Bad credit means you may struggle to be approved for a phone or Sim-only contract. Pay-as-you-go deals aren't as cheap, but crucially you won't be credit-checked.

If you want to check your credit history, you can get your free credit report and credit score by joining our free MSE Credit Club.

11. Get your phone unlocked for FREE. For a new Sim to work in an existing handset, it must be unlocked. Networks can no longer charge to unlock your phone if you're out of contract - and even if you're still in your minimum term, most choose not to. See Free mobile unlocking.

12. Cover ALL the family's phones from £10/mth - but do you need insurance? Many don't - it's all about whether you're a loser. See our Mobile Insurance guide to help decide and find top picks from £6/mth per person, £10/mth for a family - which smash networks' charges.