Complain against Finchoice service

Finchoice has treated me well for the past few years, just recently it had been a pain in my life, after settling my loan with them previous year they started to deduct my account again after few months I've settled the account and I called them in many occasions where they promised to resolve my complaint but they never stopped and now I'm very frustrated cause I have to reverse the debit order every month which is discrediting my credit record. I'm very upset cause I've contacted them many times and they promise to resolve this, even send me confirmation that its resolve; yet until now is not resolved.