Our company has never had phones
You use your own mobile, you can use skype for international calls but most people end up just buying an unlimited plan.
It's a great saving for the company. They are thinking of "bring your own lathe" as the next 'innovation'
Of course the cost of having 2 dozen engineers sitting around for 15 minutes trying to get a Skype for business conference call between meeting rooms in 3 continents with 2 people in their cars and a few fscking Mac users. Somehow isn't accounted for.