Unknown neighbor cutting my cat’s fur, what can I do?

My cat is my best buddy and my companion. I live alone. He is an indoor/outdoor cat and if I don’t let him out it all goes bad. He is a long hair black cat from a Siamese mother so he is VERY vocal. He has come home numerous times now with his fur “groomed”. He has never been injured and it’s an ok grooming job but I don’t want his fur cut and haven’t given permission to anyone. I reached out to our community pet page on Facebook but the only response I got was that “it’s illegal to let my cat outside, and a neighbor could technically trap my cat for the pound so I should be thankful it’s just a haircut.” I got an Airtag collar for him to see if that might help but it continues to happen. I don’t know who to reach out to or how to get this to stop. Please help!!