DHL poor service

As a company we deal with DHL almost daily and we have process payments begore they deliver. The department who is responsible for payment allocations is really not good at it. Either they don't know what to do, or understaffed and workloa is too much. You can send pop's to the email they tell you to, and payments still don't get allocated. And they are very quick to send your parcel to the government store if not paid in time. And try to phone and speak to a supervisor or manager, is impossible. The call centre just blocks the call. I had a call from DHL doing a service survey, i told them exactly how i feel.... And nothing further came from that. There is nowhere to complain to other than here. Sad to say but DHL is not a company I would recommend to anyone. Very poor service where it matters.