Personally, I'm always hesitant when companies offer to sponsor you a handphone with the bills fully paid by the company. Usually when this happens, this usually implies that you're important enough to warrant a handphone with you 24 hours by your side.
The problem is based on our employment contract, it usually never states that we're suppose to be on-call 24 hours a day, 7 days a week. Unless you're in a special line of work, your working hours are pretty standard. However, some companies take advantage of the fact that since they pay for your handphone and phone bills, the employee should be on-call all the time. This should not be the case. In fact, very often it's a reflection of bad management when projects go off-schedule. Having said that, there are exceptions especially in certain countries.
Anyway, the problem now is that due to the "productivity" drive, employers are increasingly trying to find ways and means to squeeze every ounce of productivity out of everyone. It's very different when your employer tells you to try the answer your phone when you can, and ordering you to answer your phone when it rings. The former means it's optional and the latter means its mandatory. And seriously, if I'm on call 24 hours, I better make sure that I'm paid for it. There are of course exceptions but it should never become a common occurrence.
Vice versa, I also dislike companies that request you to bring your own computer equipment to do office work. It seriously thins the line between personal and work life, and unless I own the company, I will never do that. In fact, if someone asks me to bring my own equipment in, I should be renting them to the company and getting paid for it. I personally never like to put any work into my personal equipment.
Anyway, back to the main topic. I always try not to contact people after office hours unless it is very critical. Why? Because I used to be on the receiving end and I know the feeling. It really spoils your whole day.