Entities can put the amounts they want except in a few bank transactions that are limited by law, such as the cancellation or early amortization of a variable rate mortgage loan or certain consumer loans".
For the commission to be legal, it must be in writing and therefore must be contained in any clause of the corresponding banking contract. Therefore, the first thing that we will have to do if we have been charged a commission for short is to read the corresponding contract (opening bank account, credit card, loan, etc.)
Therefore, in case of observing a charge in our current account for a maintenance fee, we must review the contract for which we have opened that account or card. If we see that it does not exist, do not pre-advise of this commission or that they apply an undue percentage (they charge us more than what the contract says), complain to the Customer Service Department -CSD- of the bank (we must take into account that all banks and savings banks are obliged to have this service and provide a telephone available to the customer, as well as a physical and electronic address) of the bank and a copy can be sent to the office director. Once done, the CSD must send us a written response within 2 months.
And in any case, talk to the head of our office and inform us of the requirements so that our current account has no commissions. If we do not accede to those requirements, look at other banking entities and change the account since there is a lot of competition and we can improve the conditions.