After the trigger is launched to the GS-C 180, GS-C 180 identifies the enterprise to which Party A belongs, and subsequently sends SMS message 610 to corresponding GS-E 182 (step 652). GS-E 182 verifies if the destination address of SMS message 610 is a member of Enterprise X by interrogating an Enterprise Member profile database 190. Enterprise Member profile database 190 may include records or profiles for respective enterprise members that associate a land-line number of an enterprise telephony device assigned to a particular enterprise member with a MSISDN number of a mobile terminal assigned to the enterprise member as described with reference to FIG. 2. In the present example, Party A has entered Party B's land-line number as the destination number of SMS message 610. Interrogation of profile database 190 with Party B's land-line number results in selection of a record 190b allocated for Party B that indicates the destination number is Party B's land-line and provides the MSISDN of Party B's mobile terminal 141 to GS-E 182. GS-E 182 may then modify the destination address of SMS message 610 to be the corresponding mobile number of Party B as depicted by SMS message 610 in FIG. 6C having a Destination_Num field 614 with the MSISDN of mobile terminal 141. This enables the message to be routed through the mobile network to the destination party.