SDA...if you didn't spend your credit by mistake then I agree with the orevious suggestion that Giff Gaff have taken your credit and used it as income....no one else would benefit other than you....I am on Giff Gaff and I am now seriously thinking of changing. I know it's run by its own Community so although User friendly are they monitored / regulated by the usual manner which the large companies are?
You have said before you have a Nexus device. Usually retail about £250 but you hardly use your phone and use it more as a mobile computer. Why not a Samsung tablet retailing under £90 and a cheaper Smart phone for £60-80 and Tablet much larger screen than a Nexus. An expensive device for only being used as a potable PC screen! Tablets are great in the caravan and lighter than a Laptop for weight etc.

Success!

I explained to GiffGaff that I had proof from my CPAP machine that I was fast asleep when the £15 was 'moved', that I had no intention of spending such a large amount in a month and as a pensioner I couldn't afford to throw money like that away. They were brilliant and refunded the £15 straight away. Thank you GiffGaff .

well done

Brilliant result, Andy.