Cell C is ruining my life.

How I regret taking my contract cell phone with cell c. The experience was turned into a night mere of my life. I have paid up my cell c balance, now am struggling to get a paid up letter. I call them everyday . Am being taken from Pilar to post. I send them emails they don't reply. Am in a process of buying a car, they want paid up letter from cell c which am unable to get. Please help cell c ruining my life.i hate cell,