It is the business practice of sending all clients' billing info to a separate company, who then does everything for you. It also allows a company to cut down on time and human resources spent on administrative tasks.
Telephone service companies have created a special communication service without the need to use customer's equipment. It's called a "virtual number". It also has a text type of "virtual SMS center." Thanks to the virtual link you can make calls or send messages while connected to the equipment of the company.