I havn't done it, but I have a good 6th sense/highly sceptical persuasion for newcomers, so always give a hint of being available to a regular if I am booked already by a 'stranger'. I tell them I will confirm in the next couple of hours/days ( whichever applies best), text the 'stranger' to confirm at earliest convenience..and if I hear nothing it's happy days with my 'tried and tested' already-known guy
( I don't text or contact him unless I know it won't be a problem and give plenty of time for a reply though )
In my experience, a large percentage of 'new'callers will either book several girls in advance of a business trip and simply confirm with just 1 on the day - infuriating! ( - and I have had regulars that begin to do this -they get two strikes then they are banned for ever ) also, some new callers lose their nerve as the time approaches and ' pull out' at the last minute..( gratuitous pun intended, sorry! )