What is the best way to solve a copyright problem in the AppStore?

Question

Copyright

Hello, tell me please.
The situation is this - I have stickers for iMessage. Received a letter from Apple Legal

On 4/9/2019, we received a notice from John Jons ("Complainant") that Complainant believes the app listed below infringes its intellectual property rights. In particular, Complainant believes you are infringing its copyright. Please see their comments below.
Comments from Complainant: The app maker has directly copied artwork from inside my app.
......

I found the applicant's stickers, from his sticker pack, only one of my 50 stickers looks like him. A letter was sent to the applicant with a request to clarify which particular sticker violated his property rights (Apple itself asks to communicate with the applicant directly). I didn't get any response from him. And now the question is what should I do. I have suspended sales of the entire set. If I delete this similar sticker and return the set to the AppStore again, I need to write to Apple about this situation, because they have such an item:

2. Written assurance of rights may include confirmation that your application does not infringe Complainant's rights, an express authorization from Complainant, or other evidence acceptable to Apple, and should include documentation wherever possible.

Has anyone encountered a similar situation, what is the best way to proceed?