MTN - unsolicited calls

I keep getting calls from MTN regarding the fact that I am due for an upgrade. Thanks for that! I get more than 3 calls per week sometimes. A month or so ago I requested that the agent put a do not contact on my profile. i.e. unsubscribe me please. They were very pushy and kept on trying to sell me another phone & contract. I had to re-iterate that I was not interested before they would actually listen. Funny, but I again received a call less than a week ago, even after specifically requesting I be put on a no contact list. I again requested to be "unsubscribed" put on a no contact list. Please will someone confirm that this has been done.