Disrespect and Unprofessionalism

I am a Dstv client and Im paying my premium monthly but im now annoyed by their promotions department. In a day they call me two to three times selling a subscription service that im not interested about. I even Asked them nicely that they should put a note on their system not to call me but no they call me as if im owing them . The last agent that called me this morning was worse when i start retaliating their agent said "How old am I " the agent was very very rude and unprofessional . I even think of cancelling the services I pay for monthly because I honestly dont want to be their client anymore because i cannot get two to three calls asking me same thing that i told them already that im not interested.