Dear Mrs Paranoia:
I'm fairly certain that you do not live inside a post office box. Please give me the address where your air conditioner is located. Don't ask me why, or tell me you don't give your home address out. The repairer goes to the address on the worksheet we send him. He need to go to your aircon, which is in your home. If I send him to your post office box, you will call me back and complain that it never got fixed. I don't want that. Not because I give a damn about your oh-so-precious cool air, but because I never want to talk to you again.
Now, either give me your real address, or rip your aircon out of your walls, and take it to the post office. And if you do that, it will void your warranty.