Your review is honest and useful so kudos for that, but from my experience, there is no point in booking in advance with Thai wgs, its not how they operate. Always book on the day.
Anya is a great WG. Her communication is very good when she is available because she is the one responding and not a maid. A few years back the operation in water street was terrible and there was constant bait and switching. But it hasn't been like that for a long time.
You did the right thing by messaging before you leave to confirm, I always do because I travel a long way. Having said that, you shouldn't have to if they have confirmed in real time. Always have a backup WG then it won't bother you as much if it happens again.