No city has the area code 855. It is a toll-free area code used throughout the United States and Canada. The calls are free to the caller because the receiving party pays the long distance charges.
While toll-free area codes such as 855 are used in both the United States and Canada, the owner of the toll free number may place restrictions on which calls to accept. For example, if a business in the United States does not want to accept the fees for Canadian calls, they block Canadian numbers from connecting. Calls to 855 and other toll-free area codes are not free to callers from outside North America.