I'm fighting a battle here and am looking for ammo:

Can an employer demand that a salaried employee provide his cell-phone number and be available via his cell-phone 24/7? Or (my arguement) does the employer have to provide a cell-phone? I have no problem being 24/7, but I won't use my phone for it... even if the boss says that he'll allow me to file an expense if the call gets too long (what ever that means)

thanks