Pathetic service

I get calls every month telling me to make payment arrangements on my account yet I'm ahead in my payment, I have a collection agency calling me every month for payment arrangements on an account that has a set debit order. I receive threatening sms,s. I request a settlement letters I get one amount from accounts department and a different amount from bears manager . I will never ever buy from ur store again this has been the worst experience ever, even settling the account was impossible because nobody knows what the amount be. I want the matter of this collections department sorted out. As I'm ahead with my payments and not behind I'm tired of thus