It is one thing to glance at a hot girl walking by, I know I have done that, even when I was with a girl I was dating. Little things like that happen, and shouldn't be considered a big deal.
Phone sex, is a bit much. It could be a cry for help that he isn't happy in the relationship with you in some form. It could be he has some need being met by having phone sex with this other girl.
I can tell this bothers you alot. More so then you probably are stating.
Are you happy with this relationship? do you want to continue staying with him?
if you do, you need to have a serious talk with him. See if what you want and need, is in alignment with what he wants and needs. You'll have to trust him again that he is done with that and is committed too you. Going to relationship consouling might be a good idea as well to work though things.
Hope that helps, good luck.





