DAT

When you asked them about the error, how did they justify it?

 

IF this is true and they took too much without a refund OR discount (without any fees until original amount is met), then it's theft. IF this can be proved AND you elevated the complaint to upper levels, then you can sue.

Mistakes happen. If support is being difficult, elevate the complaint. Keep logs of every contact. Keep any and all paperwork regarding this matter. If you are able, record all future calls and keep all written correspondence.

However, if they were making up for recent over-payment to you and they just ain't telling you, you have no case...but...elevating the support call will eventually yield an answer. If you have not yet done ALL that you can to discover reasoning and/or gain resolution, dissing them on a public forum gives THEM a case. FYI.