Rude Mtn agent

I only missed one payment in December last year, now i get calls every week to settle my account, I've been harassed by employees on a weekly basis *** i dont want to receive calls from this number or agent they ****ing rude and unprofessional they hand up while um talking for that reason i would like to cancel or terminate all relation with MtN According to the popia if i said dont call me you have to comply