If you're one of TalkTalk's four million customers you've until Thursday to claim a free upgrade – including free Sky Sports for TV customers or a 12-month mobile Sim – after the telecoms giant extended its deadline.

The embattled provider announced the sweetener deal for all its existing customers back in November, to thank them for sticking with it after a high-profile data hack left nearly 157,000 account holders' personal details exposed.

Initially users were given until 31 December to claim their free upgrade, but this has now been extended to 11.59pm on Thursday 7 January. You can select your upgrade by calling 0800 230 0403 or via your online account.

The upgrade offer itself hasn't been trouble-free. After it launched some TalkTalk users took to the MoneySavingExpert forum to say they'd been unable to choose a free upgrade online – though this problem has now been resolved.

Others have also complained you can only upgrade online when using your TalkTalk home broadband – so, for instance, you can't choose your upgrade while at work. TalkTalk says this isn't a glitch though, but part of "ongoing security measures" it's put in place.

What are the upgrade options?

TalkTalk customers can choose one of the following upgrades until Thursday 7 January. However, you won't be able to take one of the free upgrades if you already pay for that service.

1) TV channels – open to existing TV customers only

Only those who currently have TalkTalk TV can opt for this one for free. You can choose from one of the following TV boost packages – films, kids, entertainment or Sky Sports, which will be free for three months.

This upgrade would normally cost between £5/month and £30/month depending on the channels.

2) A 12mth mobile Simopen to all customers

Any current TalkTalk customer can choose this option – a 12-month mobile Sim. It's very much a value option though, with a monthly allowance of 100 minutes, 250 texts and 200MB of 3G data.

If you go close to your allowance, it'll send you a text message. If you go over, you'll be charged out-of-bundle fees, which are 40p/minute to call landlines and mobiles, 15p per text message and 15p per MB of data. TalkTalk Mobile piggybacks on the Vodafone network.

Normally this Sim costs £5/month.

3) Unlimited UK landline or mobile calls – open to broadband and home phone customers

For those who already have a TalkTalk landline and broadband, it's offering calls to mobiles or 01, 02 and 03 numbers (excludes 084/087/09 as well as 118 numbers) free for 12 months.

While it's 'unlimited', TalkTalk does operate a 'fair use policy' of 1,800 minutes per month (30 hours). Calls are free for the first 60 minutes only, so if you pick this option, make sure you hang-up and redial within the first 60 minutes or you'll be charged the standard rate of 11.5p/minute for landlines and mobiles. Some non-inclusive calls may be subject to a connection charge of 17p too.

This calls package normally costs £7.50/month.

4) A broadband and Wi-Fi health check – open to broadband customers

If you already have TalkTalk broadband, you can arrange for an engineer to visit your property to check your broadband and Wi-Fi and improve their performance for free. The engineers operate between Monday and Friday 7am-8pm and on Saturdays between 7am-6pm.

If an issue is found, the engineer will attempt to fix it there and then. However TalkTalk says that if there's a problem with the line, it'll need to refer the issue to BT Openreach. We asked whether engineers would attempt to up-sell to customers and TalkTalk's confirmed they won't.

The broadband and Wi-Fi check usually costs £65 for a visit.

Last chance for TalkTalk customers to grab free upgrade
Last chance for TalkTalk customers to grab free upgrade

Will I automatically be charged for the upgrade after the free period ends?

TalkTalk says there's no ongoing charge associated with the free TV or calls package options. After the free period ends, these will be automatically removed from your account and you won't be charged in future.

However if you choose the 12-month Sim, you WILL be charged £5/mth from month 13 onwards. If you want to cancel the plan before you're charged you'll need to give it 30 days' notice.

All customers also get a free improved security package

TalkTalk also says it's created a new bundle of 'online and telephone security features', designed to improve protection from scammers, malware and cold callers. This includes caller display, voicemail (so unknown callers can leave a message), last caller barring (so you can block callers you don't like), and anonymous caller reject.

The provider says customers can activate the features by calling 0800 230 0403 or via their online account.

What if I don't want an upgrade – can I cancel my contract instead?

We asked TalkTalk what would happen if customers did not want to upgrade and asked to cancel their contracts instead. As it's told us before, it says only those who can prove they've lost out financially as a result of the hack will be able to leave penalty-free. See the Four million TalkTalk customers to get free upgrade and the TalkTalk website hack MSE news stories for more information.

If you're unhappy with TalkTalk and want to leave despite the upgrade offer, see our Cheap Broadband guide for the best offers around. Top picks currently include a year's Sky standard broadband and line rent for £216, plus you get a £50 voucher, or a year's Virgin fibre broadband for £224.

Have your say