Like, 80% of the people on online sex sites, and 95% of the people on (the now dead) Craigslist.
A lot of people will play the fantasy role, exchanging pics, talking dirty, arrange for a time to meet..then not follow through.
I don't think phone sex counts as cheating. That's more of interactive porn- like webcamming. Meeting up and pursuing some sort of limited or long term relationship is cheating.