Parcel CL044412827RU with some goods that I'm returning to the chinese seller is stuck at the chinese customs. They ask for bill and declaration, how do I get in contact with them ? Where should I send declaration for customs? Inside the package there's a original order details - all the stuff and prices of the goods returned.

Tracking number: RS001435159KR
It's been a while since I sent the product, and I haven't heard anything about it arriving, so I checked my parcel tracking and it says "Waiting for Cargo Declaration Materials from Addressee" since 9 November.

When I asked the consignee, he said that the package was detained by Chinese customs and that I needed to pay $85 to get it cleared.

The information for my package is: "you need to submit customs declaration materials or go through the return procedures". How can I submit the papers to finish the customs declaration?