In situations like this, I always rely on rules, policies, agreements etc...
When someone is trying to take advantage of you they will always do it face to face or over the phone, they'll make you uncomfortable or try to affect you emotionally in order for you to break.
If you only ever speak via email (so you have everything in writing), follow the rules, and have records of payments, and evidence that you're allowed to be there - then there's nothing they can do. And that really is the end of it.
Works every time. Just make sure you get their threats, and most importantly the reason they say you have to leave in writing is that if it's unlawful, you can use it to get your money back. Or if the police show up etc.. because the hotel says you're tresspassing, you can prove that you're here lawfully.
Manipulators HATE evidence. Remember that.