Paid up letter ordeal

I have paid up my cellphone account with cell c over a year ago and I am still waiting for my paid up letter. I spoke a lot of people who keep on trasferring me and no paid up letter. I have had many contracts with cell c and paid them up. Now that I want the paid up letter they give me the run around. Cell c did not update my credit profile which affects me negatively when applying for financial assistance.