still waiting paid up letter

I made arrangements with mbd about my tv license account to pay 3 instalments over 3 months so the account will be settled. The last payment was made 25 June 2015. Since 26 June 2015 when i emailed them the proof of payment. They now until today cannot respond to my email. Instead i get a call from an agent insulting me and telling me that i still have an outstanding balance on my account. I told her that i paid long ago and emailed the proof. So my guess is that there are people working in areas and not checking the emails. I want that letter by close of business today before you guys come back and tell me i am still owing more money. I played my part. Play yours.