A computerized telephony bridge unit has a Data Network Telephony (DNT) Port and a Connection Oriented/Switched Telephony (COST) trunk port, each associated with circuitry for receiving a placing calls in the data format required by connected networks. The bridge unit further comprises conversion circuitry for converting data dynamically between network protocols compatible with each connected network. Control routines executable on the computerized bridge unit are adapted to receive a first call from one of the COST and DNT networks, to place a call associated with the received call on the network other than the network on which the call is received, and to dynamically convert data between a call connected at one port and a call connected at the other port. The data network can be the Internet, and the COST network can be any publicly or privately switched dedicated-connection-oriented telephone network. Association between calls between two otherwise incompatible networks can be by a locally-stored lookup table, by negotiation with a caller, or by retrieval of data from incoming calls. Methods for practicing the invention are taught in the disclosure.