So far this year, it happened twice to me.
1) Saw Photo/Video listed in her regular menu, so took a few pictures (she posed cheerfully) during a session. The session did not go well at all due to her fault, but after the session, she texted me that pictures were $100 extra (while I was expecting an apology from her). She kept texting me I owned her $100 and I was NOT a gentleman etc. After a week, eventually I decided to settle it down by delivering an envelope ($100) to her hotel.
2) After got home from an otherwise happy session (did not check text during driving), I received an unfriendly message that I was $20 short (a miscommunication caused by her) and demanding immediately payment of the difference. I ended up wasting more than an hour to drive back to deliver another envelope.
As a hobbyist, how will you handle this type of misunderstanding?
As a provider, what do you expect if this type of misunderstanding occurs?