New Handset Calls

I get calls from Cell C on a weekly basis to say I qualify for an upgrade and with the calls I get 50 sms's to say I can upgrade to a new handset. If I wanted to do this I will call you!! I bought a phone cash and is just using your contact. Please stop calling and every time I pick up it is a machine on the other end(If you call me DONT tell me to hold for the next available operator) I stopped answering any calls from Cell C. Please keep this up and I will move to another opperator. Thanks