Recently, several k-girl numbers I've called have worked this way:

I call, it goes to voicemail, I get a recorded message saying either "mailbox is full" or "mailbox has not been set up".

A minute or so later, I get a form text at the number I called from, with info about the next appointment and what info she needs from me for screening. So if you're calling from a landline, or texts are otherwise blocked, you might be missing these.

Dunno how common this is, but the last three in a row for me have been this way, so thought I'd share.

(Personally, I'm stuck on the next step --I reply with my screening info, and then don't get any further response. Best of luck!)

Try Thai Nana, the booker is really good