methods and apparatus are disclosed for reducing wireless telecommunication costs for enterprises having a plurality of pbx - equipped sites , connected by either a public network , a private network over the internet , etc . ), or some combination of public and private networks . in particular , the illustrative embodiments of the present invention attempt to reduce telecommunication costs by advantageously routing calls from an off - premises wireless terminal belonging to the enterprise via one or more of the enterprise &# 39 ; s private branch exchanges . the present invention is especially advantageous in that it can reduce telecommunication costs for calls from an off - premises wireless terminal to any type of destination : another cell phone , a wireline terminal , a private branch exchange , etc .