Complaint. Refund

I received a settlement letter and paid up Homechoice account and I requested a paidup letter but they delayed. End of July Nimble group debited my account whereas the account was settled . Now they refusing to refund me claiming that I was supposed to inform them that the account has been settled with Homechoice. I was never informed that I was supposed to inform Nimbel group and I feel it was not my duty as their client is Homechoice