Worst service cancelation of contract

Ive upgraded via mtn direct got great service however when i decided i didnt want the phones and took them back to a store the trouble started they say i need to cancel that and then ill be able to get other devices but now no one is able to assist in that and the call centers agents sent you from one person to the other just to no avail let messages for supervisors to call me back and also no avail complained on facedbook same story weve escalated and your ticket is still open im already paying for something i dont have and when i dont pay they cut my line ive been a loyal customer for 11 years and never ever received such terrible service i dont want to cancel completely i just need other devices why is it taking a lifetime its like we are talking to computers and they dont know what to do so they mal function and send you to other places which also cant help by all the complaints seems like mtn cancelations department is the worst