At the budget you've demonstrated so far girls are more likely to be interested in same-day bookings within a short time of the call if you're unknown to them i.e. something they think might be more likely to actually take place because a punter has the horn.
Bookings further in the future are more likely to be accepted and honoured for known/regular clients.
Girls may well not be perpetually logged in to AW, but even if they are getting notifications of bookings to their phone, the one thing more likely to be within reach than a condom, they will still prioritise calls and texts, again because that channel tends to be for those with more immediate intent.
As mentioned above (reputable) agencies are the ones to go for if you're booking in advance, especially at this sort of price point. More exclusive, successful (And reputable) indies should be more inclined to honour bookings made in advance as they understand how to do good business. Unknown over-priced "hotties" may well be just paid content scams and have little or no intent to get real with a punter.
Without seeing who you've been failing with/messed about by we can't tell you if there's anything else suspect about the girls you've chosen that you can change your search methods to avoid.
I make same day and advance bookings with mostly no hassle at all but then I have my expectations and contingencies set based on what I do/don't know about the SP.