Marketing messages spam

I receive daily messages everyday from MTNYellow, MTNReward, MTNWin and MTN. According to mtn customer service, the agent Mkgetheleng Phohlo said they cannot cancel these sms, their system does not allow it. I have even tried to opt out by dialing *130*603# but still receive these sms. These sms has become very annoying and I believe this to be spam. Please can this be STOPPED immediately.