Spam calls for upgrading control

I have a contract with MTN that I took out in 2011. Have been upgrading it ever since when due.

In the last 2 weeks, I have been receiving calls after calls from companies working on behalf of MTN to assist me in upgrading my contract.

I am being spammed just to upgrade my contract.

I think after 12 years of having two contracts with MTN, it's time to cancel my contracts.