DHL Pallet charges

Hi, We are selling on Amazon.de and are storing and shipping our products with a 3PL. On their latest invoice they are charging us an additional 76 euros, when we have queried this charge they state that it’s:
“for For pallet shipments, Amazon Germany requires a delivery slot to be booked with the carrier before delivery. DHL charges for that service.”

I have tried to look this up on the DHL website, and can find no information about it, it seems an excessive charge for booking 1 x pallet. I am querying it with the 3PL and have asked for proof of this charge, it would be helpful to know if anyone else come across this?

Thanks