No response on requested confirmation PoP

I asked Annemarie to confirm that she has received the proof of payment for the May and June installments I made on my A200. To date there has been no response from her. I still get calls from the lawyers telling me that my account is in arrears whereas everything has been paid and my account is now up to date. I dont know Mercedes to be a company that frustrates its clients like this. i am disappointed to say the least.