Irritating Promotions From MTN

<p>I've been a loyal customer of Mtn for more than 10 years but lately I've been receiving promotion messages from them after I have recharged my account and I have been calling them over 8 times telling them that I do not want to receive this messages and they gave me a number to dial so opt out of which I've done but I'm still getting those sms's and I told them that I still get this sms's and they say they are going to send an e-mail to their advertising department and ask them to opt me out and still no change and I have bee calling and I was told that they did sent emails to their advertising department. So now I don't know what to do other than port my number to another network because they are not attending and solving my problem.</p>