Advice regarding house rules violation

[Nhất-Ngọc0]

We had a situation with 2 guests from Russia who violated our home rules for late check-in.

As stated in our rules, we charge 25 euros extra for late check-in after 9 PM. 

We already warned them before the situation, and they agreed to pay. 

We have all the proofs of messages and screenshots.

We sent the 25e request to their account and asked them to accept but they returned no answer. 

They also declined all of our calls and ran away back to their home country after check-out.

We have asked Airbnb to get involved in this case (after 72 hours) and we have been waiting for the response for a week now.

Have you ever been in the same situation or had any advice to this situation?

Thank you so much!