RCS dont keep their side of agreement

I was behind with my payment as we lost a contract and were unemployed. But I did made payments but still couldn't use my account. They phoned me to make arrangements to use it again after 4 months of paying I still can't use my account. My statement show I have Availability of funds but in shops it decline. I actually don't mind because they have ridiculous intrest rates. But don't make me agree for debit order and don't keep your side of the agreement. I am self employed and don't have always funds available on a specific date.