I have a similar situation....or phones have caller ID's list the names and the time you were on the call............ I have had my boss call me from her home or desk and ask me who so and so is and why was on the the phone 1-0 minutes with them??? After all, It is company time.....I just have my personal calls come through my cell phone.,...they tell us not to use them, but if you have children in school or business, there are times you will HAVE to have personal calls.
I certainly do not like it, but I take their paycheck each payday!