Well, if they overcharged you, you have the right to be refunded.
If you don't want to call to the bank in person, you may wish to consider sending a letter by registered post setting out your complaint, what you want to happen next, and when you want it to happen.
The next step, if they fail to acknowledge you, or resolve the issue to your satisfaction is to complain to the [broken link removed].
Keep in mind that banks would have been closed quite a bit over the past while, but thy should be back to normal now.