Did you actually hear her having phone sex or are you just being jealous?? If you did ,,not to many jobs require you to have phone sex! Flirting is one thing but phone sex is another issue. Get her phone and look at her text records if they seem to sexual than something is up. But if that is all that is going on(no sex yet) than I would be blunt with her and have her quit anyway.Y'all have been married for 26 yrs maybe she just needs to feel sexy and pretty by someone else for a change to know that she's still a woman, everyone likes to think that someone else thinks there nice looking. who knows , I would also confront her boss and say I don't know what you are doing with my wife but if I catch y'all together than it will be your last day at this work or something like that I'm sure you can think of plenty to say to him.  What does she do for a living that requires none stop communication all night after work? Good luck