First: are you contacting the lady via her stated contact methods?
If her ads and site state you must use her Screening Form or email to get the ball rolling, then please don't expect her to reply to SMS texts. Just because you found a phone number for her SOMEWHERE doesn't mean you should use it. 
If she is not replying to your texts OR emails within minutes, she is likely busy with something, perhaps even with another gentleman.
Consider this: when you are in session with a lady, do you want her to be checking her phone, replying to other potential clients?
This is of course not the only reason she might not respond right away, so please give the lady a little leeway. Even if she posted, or re-posted, an ad within minutes of your text does not mean she is sitting there with nothing else to do but respond.
Especially if you're referring to BP ads or similar sites, where she may have scheduled auto-posts and and thus did not manually activate her most recent ad at the time it was posted.
The most common reason my inquirers don't receive any response are: they wrote something I consider rude or inappropriate, mentioned $, said nothing more than "hey" or "u available", inquired about something I don't offer, or in some way came across as someone I don't wish to meet.
Also, if you sent your message during a time when her schedule or calendar shows she is off.... don't expect a quick reply.
I frequently receive inquiries over the weekends, and/or when both my assistant and I are off, and then when I respond during the weekdays am told that I took "too long" to get back to them.
I'm fine with that, as I do respect needing a prompt reply; but for some reason there are gentlemen who are NOT okay with the fact that some ladies take entire days/weekends off of answering their messages. These people have often scolded me for "not taking a few seconds" to get back to them.
I can understand their POV but they have no empathy for mine, which again.... is totally alright with me as it actually shows me we might not be a good fit anyway. 
Awhile back, I posted on this board about why I might not respond to your messages and a few other ladies chimed in, so you may find that thread enlightening. Follow the link for that.....
-- Modified on 5/22/2017 9:24:28 AM
I delete these
Hi
Hola
I want to fuck you
Photos of their cocks
Wuz up
Late in the evening or after midnight requests for "are u up"
Guys in their 20s and early 30s, I have text in my site that I meet with Gentlemen over 40
Hi, how much?
You're beautiful will sometimes get a ty but no more
99 % of the time I only text the day of unless we have met
I do not list or give my number until the day before we meet unless we have an extended meeting and we are creating the seduction before the dance
