Just voice call the numbers. See if anyone picks up.
I sometimes for shit and giggles, I try booking the well known twitter AMPs from virgin-to-hobby numbers to see how anal they are about screening, VOIP numbers are routinely ignored unless I voice call the spa, ATT/TM SIM card numbers texts always get answered back in 5-10 mins, usually with copy pastes. The SIM number is less than 1-2 months old on my side.
Tipping? you mean free session? well your going to be blacklisted. I never tip unless the girls do something way beyond basic. You/me will probably never see the same girl twice. They will retire faster than you going back, its not a relationship.
Maybe all girls are busy with customers for the rest of the day, maybe all but 1 girl quit/got sick/left that day. Maybe LEO visit. Maybe THAT NUMBER is getting a text SPAM attack (you know AMPs have multiple numbers for various reasons over the years). If you are ghosted one day, message another day. Some agencies will write to you "all girls are sold out for the rest of the day", but thats some american capitalism marketing, AMPs I think just ghost you.