Settlement agreement

I currently have a loan repayment agreement which was done over the phone as stated when you call the call centre that all calls are recorded and from my knowledge my remaining balance was 10500, which I made arrangements to pay it over in 3 months through debit order for the amount of R3500

Now when I call the call centre they stated I still have 6 months remaining of me paying R3500 which to me does not make sense, I asked for the recording and their telling me they cannot find it They keep hanging up my calls which is very unprofessional because I'm trying to understand how is it that I must pay double of my current balance as per my knowledge

So I want to know how do I go about resolving it because I feel I'm being ****med and I'm not finding help through the call centre