Sky Mobile was the first network to allow you to bank unused data each month and use it at a later date, now you can spend your surplus data another way.

The Sky Mobile Piggybank Rewards scheme gives you the option to swap your unused data for cash discounts on phones, tablets and accessories.

You can get up to £50 off any device or accessory in return for your unused data. If you don't want or need the discount, you can still rollover your data for use at another time.

According to Sky, over 90 per cent of its mobile customers have already rolled over enough data to be eligible for the rewards.

They can cash in their data on Sky.com or over their phone. Different rewards will be available each month, with the current deals including iPhone cases that can be bought using 5GB of spare data, or a JBL Go 2 portable speaker for 20GB.

"When we launched Sky Mobile, we wanted to offer the best possible deal to our customers. Automatically saving their unused data with Roll was a big part of this," said Sophia Ahmad, director of Sky Mobile.

"Our customers have saved over £50 million worth of data so far, which would have been lost with other networks.  Now we’re improving Roll even more with Piggybank Rewards - turning customer’s unused data into savings on new phones, tablets and accessories."