Cell c is horrible

I had a contract with Cell c and I defaulted due to b unemployed. I was handed over to their debt collectors and paid off the account in August this year, it still shows on my credit score. I have tried everything, going to the store, I tried calling the call center and they kept giving me the run around, I was given a number for their legal department which doesn't go through, ever! I regret the day I took a contract with cell c, never again!!!!!