When the service person arrives to fix the coffee machine at the office even though no one can recall calling him, the reason is probably this simple: The machine called the service company itself using its own cellular network in order to do so.
Mobile to Mobile, or M2M for short, is a technological field that encompasses devices communicating wirelessly on an independent basis, as opposed to a device like a traditional new or old cell phone that is user driven. There are possible examples of the technology wherever you look, from the coffee machine at work to the burglar alarm that has cellular for a backup for monitoring by the central station in the event that someone cuts the phone lines, to the glucose monitor that you have to wear because of your diabetes. In addition, that is not even including that suspicious freestanding ATM you use at the convenience store.
The devices give a big boost to efficiency and save a considerable amount of money by completely automating remote management and data collection. Rather than the electricity company having to send out a meter reader to every house that uses electricity, the meter simply sends its data in all by itself.
Nor is the cost of the devices particularly expensive either as, with such devices generally not requiring high speed access, it can be achieved for as little as just $1 per device every month.