Black mailed to take another contract

I had a cell number for about 5 years. I first had this number as contract then was prepaid and went to contract again and still kept my number. Now I want to cancel the contract for financial reasons, I am told that I have to find another number if I cancel the contract. I have to take another contract to keep this number. This is a number I had when I was on prepaid now they want to take it,vodacom is forcing me to take another contact. Itslikeam blacked mailed to take another contract.