Mtn being persistent

Ive decided to not upgrade and canceled my contract with mtn 2 years ago,ever since then ive been receiving calls to upgrade and been asked to take these "great promotion" thats available and ive declined telling them rather not to call me again and take me of their data base but i still get called again,if a client request to not be called again should they not deliver what the client wants???does the popi act not protect the clients privacy if im not being removed off their call center data base???