Paid up letter.

Ingrid from MBD customer care said she will send a paid up letter in ten minutes,she even confirmed my email,ID,and phone number but she didn't send.latter in the afternoon when I try to call after realising she didn't sent she ignored my calls.i called again the following day and she picked up, when she realised it was me she dropped the call and never pick up again. I just want a paid up letter or any proof or acknowledgement that they received my money.how can that be so hard?