I just say who I am and if it's convenient to talk.
If it's not they'll hang up or say 'wrong number'
Or a text message inviting a call back.
I figure that if it's a big deal they would either:
1. Not call a prozzie in the first place
or
2. Phone me from a
Burner(They're grown-up's and can work it out)
This morning I had a call which I missed. 30 minutes later
I rang back. Spoke with Tentative Man {TM}.
TM thanked me for the call-back and asked for details
then suggested a 'maybe', later that morning.
He never completes outgoing calls* coz his wife once
sussed he had called a prozzy.....He then texted to say he couldn't make it
followed by a text 30 minutes later, saying he could.
Then followed a series of texts {which I hate}
and resulted in a client and a rather delightful session
{ie A 15%er....one of those sessions that is WOW!}
Which wouldn't have happened without a call-back.
*The wise among you will be frowning as to why an outgoing phone call
could be found by his wife
but an incoming call and a text exchange is ok 
My head hurts if I think about this stuff for too long.