No use been loyal to MTN

I am a customer of MTN for 15 years I called them to please allow me an early upgrade so I do not need to cancel my contract as I am wanting to keep my number with a cheaper device I am also willing to pay off my device to which I received a written quotation on Saturday from Sphumelelo Nozaza The amount was for the balance of the 12months which was quoted at R1573.61 .I would keep the contract as is for the balance of the period which works out to R301.62 for my package Today I phoned MTN to ask for the early upgrade which they declined I then asked for a cancellation fee as there they are not willing to help and I was given an amount of R9638.39 ?Now where does this amount come from The samsung S6 edge is an old phone ,So very conflicting figures given in writing differ by R8064.78 MTN consultant blantly told me to write to complaints if I didnt agree No assistance no customer no courtesy and to think I chose them as a service provider ,How is it Neo Makoti works in Rententions as I am sure this department is meant to keep loyal customers not ask them to leave ,I require someone to look into this, I am willing to pay the R1573.61 for the device and keep the contract at R301.62 or take a new contract around the same R250-R300 amount .