Bad service from Markams

I bought 2 phone at markams I also took an insurance for those phones. 1 phone got ****** I went to the store to claim but I couldn't receive any help my second phone cracked the screen took it to the store where the sales lady did a claim for me after 3 month I went back to enquire as I haven't received any news regarding my phone the respond I got was that those phones already passed 2 yrs so it was not going to be replaced but funny enough every month when I pay they also took money for cellphone insurance. Then I phoned wanting to cancel my insurance they person I spoke to at call center said they will cancel it but they didn't in 2019 around May I paid up my account toward month end I received a statement stating I owe Markham when I enquire they said that was for cell phone insurance. I went to the store again to ask them to check only to find out it was for both phones which they failed to replaced. After 2 month I received another statement the amount owing still it still increasing and I started receiving call every day from Markarm call centre demanding payment I have being telling them since from August 2019 that I do not owe them I keep on relating my story to every call centre agent who call. They started telling me that me not paying my account its going to affect my credit profile I called them wanted to speak to the department manager and they said he will call me back till now it's 2020 June they still call me and the manager never got back to me its frustrating me especially when coming to the point that it's going to affect my credit profile please help