Bad service

I had Rcs credit with pick n pay smart shopper card. I paid up the what I owed mid March this year and I was told it takes 36 working days to close the account and I couldn't believe that as it took them two hours to open the account for me, I kept pushing and end of March I was told the account is closed and I asked for the letter that confirms that the account has been closed I haven't received it to this day, I called again 3 weeks ago I was told it would be done in 48 hrs, I still haven't got it.