DHL negligence

I have a package stuck in customs. An agent emailed me and told me all the relevant documentation was attached "for my convenience". I sent 2 emails with all the relevant information 2.5 weeks ago and never received a reply. Now SEVENTEEN days later I emailed to find out what the delay is and the implication is that I never filled in the documentation! I have ordered these items many times before and have had many orders delayed but never was I expected to fill in and pay fees before - isn't that the clearing agent's job. And if it's the customer's responsibility why wasn't it made clear from the beginning and why was there no reply to all the supporting documentation I sent in????