Paid Up Letter

I requested a paid up letter on the 02nd of April 2015 as my account was paid up on the 27/03/2015 , when i went to Jet @ the Randburg mall , I was told that the was an outstanding amount of 28.00 which i paid on the 02nd of April.I was told that the letter will be emailed to me in 48hrs, but the letter was never emailed, I went again to request for a letter on the 14th/04/2015 was told it will be faxed to the store in 48hrs. I went to Jet again yesterday @ Randburg the was no letter, when we called the call centre i spoke to Carol, who told me that the paid up letter was faxed to the store on the 16th however the is an outstanding balance of 1rands, I am confused now because the account keeps on accumulating balance on the other hand i am told that the paid up letter was already sent .I feel like a fool now because when i question why the account keeps on accumulating balance, Carol told me that i should call the lawyer's to ask why as she doesnt know why, what must i do now to sort this out.