Cell c

I had a contract with cell c in 2015, I couldn't pay my account due to circumstances and it was in bad review and I was handed over to their lawyers. In 2019 I managed to pay off the account and I have the paid up letter. Now am trying to get a newly contract but they reject me due to the old account. I've called and email their legal department and cell c support but still I cant get help from them...please assist me on this matter.