MTN STOP SPAMMING ME

i want to please complaun about MTN that is sending me around 50 smses per day to TOP UP .. WHICH I DO NOT WANT TO DO .. as well as push messages to TOP UP which blocks everything .. how do i stop this pleeeeaaasse .. u will buy data if i need it .. but this is rediculous .. please .. MTN stop spamming me .. i DO WANT YOU AIRTIME IF I DECIDE I NEED IT .. please stop sending me 50 smses and push messages a day .. it makes my device unworkably annoying .. STOO