Mtn been horrible to me

I bought a contract phone and after paying for it mtn still gave me minutes nd data not knowing that I should still pay for them because I thought that after paying your contract thats it. Well they gave data nd minutes monthly for like 4 months then my calls were suspended saying I should pay an amount of R480 I paid it nd I called to cancel the contract they Said they will help after I have paid the R480 I paid it nd called again to cancel it they said I should pay R150 for this month's bill nd bill which I never used nd I called them before the bill was issued to me. Am done with mtn done done