Stop Sending Me These SMSs

I have called MTN 4 times in the last 2 weeks asking them to unsubscribe me from these emails:

Y'ello,Get Double your Bundle. 30 Min FREE on buying 30 MTN-MTN Minutes for R10 valid for 7 Day. Dial *142# & select DOUBLEVOICE to buy now. Ts&Cs

Every time the call center agent tells me I have been unsubscribed but I keep getting the SMSs and I get them every day. Like seriously MTN??? What more do you want me to do?? I don't want these SMSs. Maybe I need to move both my numbers to another network because this is not on. If you cannot honor a simple request like this then what am I still doing with you guys????