trying to cancel my contract is a nightmare

i have been trying to call into the call centre and cancel my contract that has ended last year with mtn but it is a nightmare, i keep having to call in and speak to a consultant, he/she then transfers me to the retention's department that never answers, the music keeps going on and on but no answer and this has happened on numerous occasions, this is highly frustrating and a waste of my airtime to keep having to call in for nothing and not getting anyway.