A number of former Sky TV, broadband and home phone customers who were in credit when they left the provider may be in line for a refund.

Sky said it began sending letters at the beginning of this month to some customers who left the telecoms giant before 2012 explaining that they're due a refund. It will continue to send letters to affected customers over the next few months (see our Digital TV Deals guide for the best offers).

We asked Sky why customers had not been refunded much earlier and why the issue has only now come to light and Sky said these letters are part of an "ongoing piece of work" that began some months ago, in which it's doing its best to contact affected customers to refund their credits.

It also won't tell us how many people are in line for a rebate, but it says the average repayment is less than £10.

Sky did tell us, however, that possible reasons for the refund include customers having a credit on their account that had not been fully spent, or having cancelled their contract mid-way through a billing cycle.

Do I need to do anything?

The letters list a free phone customer services number – 0808 101 4437 – so you can get in touch to get your money back. Sky says there's no time limit for claiming the refund and it couldn't tell us how far back the claims relate to, just that it affects customers who left before 2012.

What about customers who left after 2012?

Sky says it has already been automatically refunding customers in credit who left it after 2012.

I thought this was a scam?

We were initially alerted to the issue as former customers who received a letter through the post thought it might be a scam to get their bank details. A Facebook post warning about a 'Sky scam' was shared nearly 90,000 times on the social media site before it was taken down yesterday.

But Sky says this is a legitimate letter looking to reunite former customers with outstanding payments. If you get a letter, call the freephone number to discuss your existing account and any amount you may be owed.

Remember to always be vigilant and to watch out for potential scams. See our 25 Ways to Stop Scams guide to protect yourself.