Bad Service

I have been advised by STD bank that my account was handed to them at the beginning of March and they gave me a settlement account when I called them in which I paid at the end of March

My Issue is I haven't received a paid letter & we are now approaching the second month, My first follow up was on mid April & I'm told that I will receive it every time I call. I don't understand why does it have to take this long for me to receive it & its affecting my credit profile