I asked this question a little while ago. I have only done a few incalls and out of those i only had one who gave me his full name. I always had their mobile number and sometimes a landline if they first called from home but that was it really. There isnt a lot you can do about it i suppose.
Its more important, i feel, to make sure you have your security in place. As in, letting someone know you have a booking, when its over etc. will pm you what i do incase there are any wronguns reading that i dont want knowing all my secrets lol (not even my secrets, just advice i was given by various people)