Minimum payment on loan decreased without my knowledge

I'm beyond frustrated with Standard Bank, I have a loan with them and they've decrease my installment without any notification and reasons why. I have been calling to try and get information on why this was done because it will affect my payement term also this means more interest will be incurred into this loan, I've been promised by the no of bankers that they'll come back to me but not one of them do. I have run out of options but to move to another bank and ask for a new to settle this one so that I can stay to my plan of repayment. Another annoying part is that I cannot make extra payment on this loan 😒 reasons be it's a term loan and no extra payment can be made except for debit 😫but they decrease my debit order. I have plans and I like yo stick to them when it comes to money and Standard Bank is messing with me. Where can I report this? The minimum payment was decreased yo the lowest payment without my knowledge 😭