Dude you are literally one in a dozen. These girls have many guys contacting them daily for services, some nobody John is not going to break the bank for them.
I honestly find it laughable that you think $300 is gonna hurt her in any meaningful way. Many of these girls are making a surgeon's salary, while most of us have to save money for a quick one hour appointment.
I think once you guys realize how much power these girls have over this market, you'll understand why they're snappy like that. They can afford to be. They're not waiting on any of us to pay their bills, unless they're seriously mismanaging their money.
Go to places like old.reddit.com/r/sexworkers/ and see what these girls are thinking about us in general. Most of them would rather we just give them money and leave. They are disgusted with dealing with any of us in the first place, and you think we can have the audacity to start making last-minute requests?
But yeah as you realized, you can easily contact another woman and see if she will fulfill your requests.