Unprofessional Poor service!

I recently made use of DHLcourier service and paid the driver in cash when picking up my parcel. I then requested a cash receipt for the amount paid but ABSOLUTELY NOBODY can assist with this simple request. My emails are being forwarded from one person to the next with no response if I don't follow up on the mails, and then it simply gets forwarded ton the next person. It's been going on for a month now. I then logged a complaint on their website where a response is promised in one work day but still after a week NO response was received