Annoyed MTN customer who gets spam called by MTN repeatedly every day

I get about 9 calls a day from an 031 number.. Early in the morning and even in the evening.... when I finally answer.. it's MTN... and they keep calling despite me saying no to whatever they're trying to sell me. You harass your own customers... and I have to block your number to stop you. Why do you do this? This is unsolicited and I'm getting tired of clearing my blocked calls call log... I will move to another service provider if you continue to spam me.