TalkTalk Mobile customers will not have their mobile contracts renewed and will instead be offered an O2 deal - but don't assume it's the best one for you.

Customers who are reaching the end of their contract, or are currently out of contract, are receiving emails saying their TalkTalk Mobile deal will not be renewed and they can instead move onto the O2 network, or switch to another provider.

Any existing TalkTalk Mobile customers who choose to take the new mobile deal will in effect become an O2 mobile customer, as they will be billed by O2 and go to it with any problems. While TalkTalk is no longer taking on new mobile customers, other TalkTalk services, including broadband and TV, will not be affected.

TalkTalk's step back from the mobile market was rumoured last year as the group said it had "reassessed" its mobile strategy, and would instead work closely with O2.

For full help on how to pick the best deal for you, see our 30+ Cheap Mobile Tips and Cheap Sim only Deals.

'I was called out of the blue and asked if I wanted to be connected to O2'

TalkTalk, which only ever offered mobile contracts to its existing broadband customers, first began offering O2 deals in December, but more customers appear to be receiving their emails this month.

Paul Elliott, 35, from London, who has a rolling Sim-only deal with TalkTalk, got in touch with

He said: "I got an email the beginning of last week saying there was a fantastic new offer on O2, with 4G and great savings off an O2 tariff.

"It felt like it was a good news story and then I clicked through to my account where there was another bit saying they will not be renewing my contract, but it doesn’t really make it clear what is going to happen to my tariff if I don't make a change.

"I was then called by them out of the blue on Saturday and they asked if I wanted to be connected to O2."

Other customers have been tweeting TalkTalk about the change:

What is happening?

TalkTalk says it's "business as usual" until customers reach the end of their contract.

At the end of their contract the customer can choose to move to a new O2 deal OR switch away to a new provider. We've asked TalkTalk if there's a cut-off point by which you must make a decision, but it says a date has not yet been set.

If you try to change your TalkTalk Mobile contract mid-contract - even if it's to O2 - you will still be charged termination fees as normal.

If you have a TalkTalk Mobile deal as part of a bundle contract with the firm for other services such as broadband, your contract for all of them will continue as normal, but at the end of it you will have to decide whether to go for the O2 mobile deal or switch away. You would be able to keep your other services with TalkTalk if you want to. See our Haggle with TalkTalk guide for tips on how to save.

How do I know if I'm affected?

Anyone who is a TalkTalk Mobile customer will be affected and will be contacted throughout 2018 by the firm.

What are customers being offered?

TalkTalk says existing mobile customers will be offered "a special deal from O2" - which some have reported to be 25% off certain tariffs. The O2 deals will also be available to TalkTalk broadband customers.

The new O2 deal will mean customers have 4G rather than 3G, and access to O2's 15,000 free Wi-Fi hotspots and the O2 Priority app.

A spokesperson said these deals for TalkTalk customers moving to O2 will change throughout the year, so was unable to give details of exactly what will be offered.

How do I check if it's a good deal?

Firstly, check exactly what you are being offered as part of the O2 deal via TalkTalk, ensuring you check the length of contract and how long any discount will be valid for.

Then benchmark it against the best deals - see our 14 Mobile Contract Tips, Cheap Sim only Deals and Best Pay-as-you-go Sim Deals for more information.

You will need to call TalkTalk on 0345 172 0044 ask for your PAC code (even if you are moving to O2) to ensure you keep your phone number.

What does TalkTalk say?

A spokesperson said: "As part of TalkTalk's simplification, we're changing how we offer mobile services. This agreement with O2 gives TalkTalk customers access to a wider range of great value 4G services.

"It's great news for customers and allows TalkTalk to continue investing in our fixed network, delivering even better landline, broadband and TV services."