If Amber is the assigned scheduler for that shop, as far as I know, you're stuck with her.
My scheduler used to be ulta-responsive, now I wait 3 or 4 days to hear from her. So I feel ya, and I sympathize. I think she spoiled me with a couple years of getting replies within half an hour, LOL!!!
However, one ploy seems to work -- I "forward" the e-mail I sent earlier (I wait 24 hours) and in the "subject" line, I put "May I have the courtesy of a reply?". I have even been known to add "URGENT -- I'm working on a route and need an answer".
It really irks me, too, because I'm their sole shopper for a route that takes me 175 miles from home and fills 4 "orphan" shops on the way there and back. So I have to plan for a day with a minimum of 6 hours drive time, and if I don't get all 4 shops, it's not worth it to me.
And I really do need an answer, because my "filler" shops might disappear if I don't get them scheduled, too.