Curious what  message should be recorded on your hobby cell phone the ladies  hear when they call  you back, as the phone probably won't be on.
Something tactful  to the effect  you desire  to speak with them but don't know how long it would be  before you can call back..

As far as a client's outgoing message on their hobby phone, I would support having their first name and let me know that it is a safe line to leave a message on.  I hate to leave messages when I never know who might be checking them!

It's a quandary,

I understand why a provider would not want to leave a message if they hear the default voicemail greeting.  It's smart not to.

For married men the issue is that they don't want their voice or name on the greeting in case the phone gets discovered by the wife.  If it is a generic greeting then they can plausibly (hopefully?) claim to have found the phone and just tossed it into their briefcase.

Hi This is Bob..
I am in for my monthly STD testing.. I will get back with you as soon as I get out -

How about "Hi, this is Hugh - unfortunately, I had an accident, if you know what I mean, while looking at the gallery on your website with my pants down - I'll call you in a few days when I recharge."