bad service

I paid my account on the 11 March 2016. and I have requested a paid up letter on the 14 March 2016 to show that my account was settled in full. till today on the 14th April I haven't receive any letter I get promised everyday that is going to be sent to me but nothing happened . I am very frustrated with the service that the gave me . I use my airtime and my time . it was a waste of time dealing with them they don't even care or understand .