Accounts

I've opened an account with Markham since 2017 I just forgot the month that I opened the account, I've been paying for the account since the first month, but then 2019 my job ended in 2019 then I started paying R200 or R300 monthly, knowing very well that I was owing R1500 in my balance. In 2019 I took clothes then the balance came to R2590 then I continued paying the account R200 or R300 then January 2020 I noticed that I'm owing R900 then I received a call from the accounts department they were telling me I must pay R80 monthly if I want to finish my debt, then I continue to pay R200 and R300 but in February I checked my credit then boom I was owing R2500 which I don't know were it's coming from, then I went to Markham Mvusuludzo Mall, the workers there didn't even bother to assist me, they told me that the can't access me to my account to check my problem and they told the they can't help me, so please I need help with why was I owing R900 then now R2500, all I want is to cancel this account and get rid of it because I'm being ******, I was faithful paying my bills but every time when I check my credit I'm still owing thousands and Rands which I don't know where they come from