Gatvol with Mtn

After numerous calls , emails etc this company don't give a s#$@t about there customers , they are only in for the money , I want my contract cancelled which was only a sim card which I took out from them in 2017 , now suddenly they told me I have a 36 months contract with them and I send me a device as well ????? I have apparently done a upgrade as well according to them ??? . I have two other phones from their opposition and barely use this Mtn phone , is only as a back and emergency's purposes , their staff is very rude and don't give you a chance to explain my problem with them . I am seriously gatvol for this company and won't ever do any business with them at all