I fell cheated when I use your plataform. You should edit the amount and not charge commission when people pay with its bank account.
When people select to pay with its checking/bank account, you should take away your commission automatically from the invoice or do it the other way around like the other payment sites: charge your fee if people decide to pay with credit card. Otherwise people feel cheated. It is very convinient to you to charge commissions when people pay with their bank account, It is not OK