I am BOMBARDED with Promotional SMSes

I have been bombarded with MTNyello SMSes for months now. I have already contacted MTN help line several times with no help. The first time I was given a number to unsubscribe (*130*603#) I followed the instruction which at the end required me to recharge to complete the task. After all that I continued to receive the SMSes.... Today I called again and the lady gave me another number (*121#) the irritating part is that when i dialed that number and followed the instruction it led me to advertising which has only two options 1 OPT-IN 2 HELP..... No Opt-out Please guys sort this mess up because it is affecting my business response time.