Contract cancelled without my request and unknown owing balancce.

I went to MTN store to enquire about my contract they told me to come in April as my contract expired then. But when I went to MTN during the expiry of my contract what I needed was my contract to continue as it and didn't have a problem with it. A consultant in Kolonnade shop they told me they can offer me new 2 cellphones , I did explain to him I don't need new phones, He made application and told me he will call me and never called. Later in weeks I received a call from MTN that I must come fetch my order from the Kolonnade shop. When I went there on that day there was a debit order trying to take money from account amount of R781, but when I went to Kolonnade they told me my application did not approve and they will lodge a complaint for me for my contract to stay as it was(Data Contract). . . I was surprised later when I went again to MTN shop and found out I am owing MTN R2553,But the service was stopped and no application was approved I still need MTN to keep my contract as it was as I NEVER had a problem with it.