Airtime recharge sms spam

Good day<br> I would like to request help in term of spam sms's that I always receive after recharging airtime. I receive more than 12 sms always for each recharge.Im using an mtn network my number is *** of which I contacted customer care and I was advised that this sms's cannot be removed as they are on their database for all mtn numbers, they cannot remove one specific cell phone number. I never use to receive this kind of sms's its been a while now getting this sms's.I would be happy if my number can be removed from this promotional database they call, I would like my number to be back to normal. This sms's they really irritate and they fill up my inbox and blocking my important sms's because at sometime I don't get time to delete them immediately as one can be very busy at some point. Surely this can be done it really inconvenience me, im not impressed at all. Thank you