Calls from one phone to another are now using the hierarchical infrastructure provided. It is assumed that a registration area keeps a record for a phone based on the phone's name. If this record is a pointer to another registration area, then searching will continue from within the pointed-to registration area. If the pointer is a pointer to the cell phone, then we assume that we have reached the cell that currently contains the phone, and thus the searching is complete and the call has been established. If the root of the hierarchical system is found and no records for the phone have been found, then the phone is not within the coverage area, and thus the call could not be complete. The read cost is aggregated on the caller's phone object. It might be necessary to also have seperate records for the read cost of individual events, such as moving and phone calls