Cell C
Need to upgrade/migrate to other contract/plan

I'm trying to contact Cell C customer care from past 10 days and no response.
I have an existing data contract with Cell C. Now I want a new contract/upgarde and cancel the existing data contract, as I don't need the data contract. I don't know the process, and tired of calling customer care where there is no response. How to cancel the existing contract. Please help me.

Regards