Opt Out Option Repeatedly Dishonoured

I recently ported my contract from Altec Autopage to MTN. I signed a new contract with MTN at the beginning of September. I selected NOT to receive marketing. Since then I have received FOURTEEN marketing messages three of which were on the same day! Only the last four of those contained an opt out option which I used. I received confirmation that I had been removed from their marketing list each time only to get more marketing within 24 to 48 hours thereof. I sent them facebook notifications and requests for removal as well as emails all of which saw me assured by staff that I had been removed. Still getting spammed. Today I got an sms saying my data bundle expires in 48 hours. What data bundle?! I never bought one and don't want one. I am unemployed so could not buy such a thing even if I wanted it. My contract, paid by my spouse, contains data and I am linked to his package should I run over. MTN seems incapable of solving this issue and they text from an unblockable number so I can't even add their number to my spam list which is automatically rejected. I am an MTN customer of 15 years now and very disappointed in this poor service!