Trying to make an appointment as a first time customer with another agency.
The ad says "call" but the voice mail is not set up, so you can't leave a message.
That means you text instead,  even if it says call?  

Every cell phone plan comes with text messaging these days, right? So it's impossible for a text not to go through?

You'll probably get a reply or some sort, but text with basic info listed here many times.  If you're nervous about texting,  try calling again later or the next day, and maybe they'll answer.

I haven't bothered making a call in years.  The last time that I did, I was in the process of leaving a message (a rarity) and received a text telling me to text instead.

texting is okay, even if they say call.  Bookers often don't answer a call live if they don't recognize the phone number.  Texting your info gives them time to work on verifying you.

Before number porting was mandatory, people changed companies, phones and numbers a lot. How many times did your idiot friends forget to set up VM on their new phones/plans. Send a text: "Hay, Moron! Set up your VM!" or the occasional "Your VM is full! Delete some messages, for crying out loud!"  

You don't even have to refer to a service: "Trying to leave you a VM but your service isn't set up. Thank you.

You don't say how you completed you screening. They may not know what your number is and so will not answer. I often get the "no voice mail setup for this number" but then get a call back as they know my number and see it pop up on their call list.

There is no harm in texting, even something totally innocuous, just as you would send such a text to a friend in the civvie world. Once they get the text, they can either set up their VM, take note of the caller's #, call or text him back and so on. Even ignore him completely!  

The first text and contact should not be explicitly about "business". Once you and the phone girl or booker are connected, then you can mention seeing an ad or making an appointment, etc., as appropriate.