Telkom Harrassment (Serious)

I have 3 cellphone contracts (myself, my partner and my mother) and my cellphone contract has ended, however I have remained with Telkom on the sim only deal. For the past few months, Telkom has called me literally twice every day telling me to upgrade. I have spoken to probably all their consultants saying im not interested however each day I still receive these calls. This is basically harrassment and I will be taking up legal matters if this continues.