Whats the tiny black box called which Rogers installed for our home phone service?

[Belimmy RAWR]

A couple of years ago we changed from Bell to Rogers. When Rogers came, they installed the phone service which also included this tiny black box. What is the box for? and also is it needed for Rogers internet? We changed our phone service back to Bell but not our internet (which is still using Rogers.) do I need to bring the box back to the Rogers company?