parties in communication this request is transmitted at step 24 to the gsm umts cellular network that provides a service of locating subscribers 3 upon receiving this call at step 26 this locating service determines at step 28 the geographical coordinates of the terminals a and b and calculates at step 30 the distance d that separates the two terminals a and b at step 32 the caller a receives the calculated distance d and compares at step 34 the distance d with the value r representing the coverage of the second network that may be as much as several dozen meters 4 at this step the network selection module 6 of the terminal a determines which frequency band is to be used for carrying out the next call in the following manner if the calculated distance d is greater than r the module 6 selects the gsm umts network at step 36 if the calculated distance d is smaller than r the module 6 selects the second network at step 38 5 once a telecommunication network is selected the software program initiates a call according to the protocols associated with respective networks in a variant embodiment in which the terminal a knows a priori the position of the terminal b the selection between telecommunication networks may be made manually note that there is a great number of service providers that offer the possibility of finding out the distance that separates two mobile terminals in communication see for.