72 contract signed.

I had a contract with STD Vehicle Finance from 2013 and they have never send a statement through to me and I remembered that I signed a 72 contract with them. I am the one who phone for my balance and I called in last year in October or November to find out about my balance and they told me is R20 000 knowing that June will be my last instalment. I called in June 2019 and they said it is R20 000 again. I have been speaking to the supervisor Prenesh and he referred me to Mpho. They have never called me that my account was in arrears in January 2014 and they have never send a statement regarding my account. they said I did not pay for December 2013 and they did not call or send a message that my account is in arrears, and I would have arrange for that to cover the instalment but they did not and now they are saying my account is extended by three months until September 2019 without my arrangement. I am very much disappointed with the service and I am not going to pay them because I was not even aware of the arrears. Your assistance will be highly appreciated.