empty promises

I had a loan with African bank and fell into some unforeseen financial difficulties shortly after. anyway I was in contact with them at the beginning of January obtained a settlement discount and paid them just over R15k to free of the debt on the 7th of January and was told that I would receive a paid up letter within 20 days. I have made calls to them at least twice a week only to be told that they will call me back by the end of that day each time, and still no call. The last call was last Friday when I was promised by the supevisor in charge that I would have a paid up letter mailed to me by 2pm, which still hasn't filtered through. how much longer do I have to wait for this? African bank you guys keep hounding us for your money, but are extremely poor at customer satisfication.