A cellular/wireless foreign subscriber is enabled to use her/his own cellular/wireless telephone instrument in a local cellular/wireless (C/W) network/system by entry of a code and a PIN into the local network/system desired to be used. The local C/W network/system algorithmically responds to the code and PIN by changing characteristics of the radio equipment of the local C/W network/system to accommodate operation of the subscriber's cellular/wireless telephone instrument with the network/system desired to be used.