Contract cancellation

I have been trying to cancel my contract with MTN since last month the 22nd of FEB 22' but no one is willing to help. I went to MTN Store at Springs mall and they informed me to dial 135 for the cancellation. I did what they told me but the number didn't go through with an error message of "server error", I keep on trying to call the number for days and didn't win. I went back to the store and they told me to email to retrentions they will help. Sent the mail to retrention as informed and I got a automatic response that someone will call me and help me out the contract ***. I waited for weeks for their call but no one called, I then went back again to the store, they help me out and told me to wait for the call from retrentions and if they don't call I must email them the reference, REF: ***. I waited for days again but no one called me, I then emailed them again as informed and I got the same response to wait for someone to call me, ***. I'm still waiting till today!