I bought an add on for £12 -, but they charged £15 where I now have a £12 add on and credit of £3

[Jurgen]

I bought an add on today for £12 of 10GB, but have been charged £15 and now have credit of £3 which I don't need since calls are included in the add on. Why was this happening? 

[MZone]

Contact Customer Service here as we have no access to your account as it’s a community forum.