Serious harrasment from call centre agent

i have a loan with old mutual of which I made arrangements with them on my monthly instalments. I spoke to an agent by the name wayne who handed the call to his supervisor, she confirmed that my loan payments will be updated correctly and I will not receive any call from old mutual and debit order will go on the 25th of every month. till this day the agents are still calling me, they REFUSE to listen everytime I try to explain to them that I have made arrangements and my account is in order. old mutual agents are definitely not trained properly because they refuse to hear they want to be heard. I spoke to an agent by the name of anelisa or something but the name starts with an A with seriously bad attitude, on Saturday the 3rd another agent phoned with the same horrible attitude. can some senior management at old mutual listen to the calls made and attend to this matter and also go through my account with them thoroughly so that these agents can stop calling me please. I am tired of being harassed by these agents.