226 via a service control point scp 228 to obtain the required information with which to complete the call to the ported subscriber one suggestion would have the originating access provider ssp 212 make a query to the database 226 for every call this is impractical as the current ccs7 signalling network could not handle the resultant volume of traffic or would be too costly and as the majority of numbers will not be ported in the foreseeable future another suggestion which attempts to obviate the impracticality of the first scheme proposes that the originating access providers ssp 212 attempt normal call completion to the terminating access providers ssp 216 as specified by the calling number when the ssp 216 determines that the called number has been ported it either a returns a release message with a cause indicating that the number has been ported or b makes a query to a database 226 to determine the address required for completing the call to the subscriber 224 via the ssp 222 representing the ported access providers in the case of option a the originating access provider ssp 212 makes the query to the database 226 to determine the address for the ported subscriber 224 in the case of option b the address is provided to the ssp 212 by the ssp 216 in the representative ain network of fig2 this scheme appears to work well with either option because there is only one database 226 in a practical system ssps 212 and 216 would not likely access the same database necessitating multiple.