How do I get rid of MTN spamming me ????

I am a pay as you go subscriber at MTN for at least 18 years. I hate spam, and MTN are spamming me. They feel they can, since I am an MTN subscriber, I say no, I don't want any promotions from you. Can MTN please explain why I can not get rid of their spam.<br> <br> The latest MTN spam outbreak. From 23 Feb I get this message :<br> MTNReward. Yello! Recharge now & get 10X your recharge value FREE. Example R2 recharge gets R20 FREE MTN-MTN Airtime valid for 14 days. Offer valid till 05/03/2015 T&C's<br> <br> I got this same SMS at the following times :<br> 27 Feb 07:09<br> 27 Feb 06:53<br> 26 Feb 08:53<br> 25 Feb 06:10<br> 25 Feb 05:16<br> 24 Feb 09:52<br> 24 Feb 09:36<br> 23 Feb 09:25.<br> <br> See how early in the morning they send some of these SMS's, waking us up.<br> <br> I am disgusted. I WANT MTN TO STOP SENDING ME SMS'S. If I want promotions I will go look on their website and in the media. I am registered at the DMA to not receive Spam, yet MTN ignores this.<br> <br> I want this to stop else I am leaving MTN.<br> <br> REMOVE ME FROM YOU SPAM SMS LIST, PLEASE !!!!! I did ask nicely. It gets to the point where I want to puke if I see the yellow MTN advertising.