You can enter the syx9002 upgrade program on the Data Fix screen (see SY Data Fix Screen) in System > Toolbox > Data Fix to run through all Employees and update their Employee Home and Mobile phones from appropriate Personnel records.

SY Data Fix Screen

Running in Undo mode results in a report showing you which Employees will be processed when you Commit the report. A warning appears for those Employees who already have phones filled in with values that are different from the Person's record, as shown in Data Fix Undo Report . Once any issues are resolved, you can run the report in Commit mode.

Data Fix Undo Report