Supermarket Sainsbury's is axing its mobile phone service in a move affecting around 150,000 customers.

The chain says its 'Mobile by Sainsbury's' SIM-only service will end on 15 January 2016, just two and a half years after it set up the joint venture, which sees it 'piggyback' on Vodafone's network. See our Piggybacking guide for more on which network provides your service.

Here's what Sainsbury's move means for you.

I'm a contract customer. What's happening?

Contract customers on a fixed length deal, which they pay on a monthly basis, can continue to use their plan until 15 January, after which it will no longer work.

If your contract ends after 15 January, Sainsbury's will only bill you for the plan until 15 January. You won't have to pay for the remainder of the contract after 15 January.

Sainsbury's says it's never sold handsets tied to Sainsbury's network contracts, so no-one will need to return a mobile handset.

If you want to cancel your contract, Sainsbury's says you can do so penalty-free at any time. It says it will waive the usual 30-day notice period and any early termination fees. See our Cheap Mobiles guide for how to get the best deal if you're thinking of switching.

I'm a pay-as-you-go (PAYG) customer. What's happening?

PAYG customers can continue to buy top-up credit until 14 November for use until 15 January.

Sainsbury's advises customers to use credit by 15 January as you won't be able to do so after this date. But it is understood that customers will still be able to reclaim any outstanding credit after that time. Sainsbury's says customers should call it in this scenario on 0333 313 1150.

If you run out of credit after 14 November but before 15 January, you'll still be able to make calls to the emergency services.

I'm a rolling bundle customer. What's happening?

If you have a rolling bundle, which is a 30 day package that renews automatically, this will operate as normal up to 14 November. After this, it will no longer renew automatically and Sainsbury's says it will remove your payment details from its systems.

For example, if you have a rolling bundle starting on 1 November it will continue as usual, however no further bundles will be applied after the 14 November.

Any queued bundles will become active as normal, although you won't be able to queue any more after 14 November.

I've got a Sainsbury's handset. What's happening?

Sainsbury's says it never sold handsets as part of a Sainsbury's network contract, although it does sell handsets on their own, and handsets alongside contracts from other networks.

It adds that all of its handsets can continue to be used as normal with a SIM card from any mobile network.

Its network of 38 in-store phone shops selling mobile phones and accessories will remain unaffected and Sainsbury's will also continue selling handsets in more than 300 stores.

So if you have a problem specifically with your handset, you'll still be able to take it to Sainsbury's.

Can I keep my Sainsbury's mobile number?

If you want to keep your Sainsbury's mobile number, you need to ask the supermarket for a PAC (Porting Authorisation Code) by 15 January so you can move your phone number to a new network. You can call Sainsbury's on 0333 313 1150 to do this.

Sainsbury's says it won't give out PACs after 15 January, so you'll lose your number if you don't ask for one by then.

Once you have your PAC, it's valid for 30 days and you must give it to your new mobile provider within this time.

Sainsbury's to axe its mobile service: What it means for you
Sainsbury's to axe its mobile service: What it means for you

I've got mobile insurance from Sainsbury's. What's happening?

Sainsbury's says insurance purchased in one of its phone shops will still be valid against your handset.

Why is Sainsbury's closing its mobile service?

Sainsbury's says the service is closing, as despite negotiations with Vodafone, they were unable to agree over the future of the service.

It adds that all mobile customers who have used the service within the last 90 days and have linked their phone to their Nectar account, will get double Nectar points until 14 July 2016 on eligible Sainsbury's shopping and fuel purchases.

A Sainsbury's spokesperson says: "We regret that Mobile by Sainsbury's, a joint venture with Vodafone offering a mobile phone service to Sainsbury's customers, is ending, and the service will no longer be available from 15 January 2016. 

"Our priority now is to help our customers and make sure they are inconvenienced as little as possible. We will continue to sell mobile phones and accessories in our 38 in-store phone shops and to sell handsets in over 300 of our stores."

The closure of 'Mobile by Sainsbury's' marks the second time the group has pulled out of offering a mobile phone service, having previously launched Sainsbury's One in 2001. This was rebranded before ending in 2003.

See Sainsbury's Q&A for more information on the closure.

Additional reporting by the Press Association.