Of course you can turn them down. If we’re talking about an amp and you only want a massage, just say so. In fact, if you just keep your underwear on, they probably won’t even try. If you’re talking an independent provider, my go to move if I get to the room and then change my mind and want to leave is to pretend I forgot the money in my car. Of course, they’re gonna let you go get it. Then you take off. (Obviously this is before any services are rendered. You’d be a scumbag to skip out on the bill after you’ve been served). If the provider doesn’t exactly live up to her photos, or something seems unsafe, you can absolutely leave and you should.