Philips DECT515 User Manual page 57

Service code settings
When you subscribe to extra services with your operator you may need to set some codes in your
phone.The default codes are the codes used by the main national operator.
If you subscribed to another operator you may need to change the codes.
Contact your network operator for more information on the services.
Press to enter the carousel menu
Scroll to Base station and select
Scroll to Service code settings and select
Browse the list of services and select
Enter the code and press
56
OK
Base station
http://www.philips.com/faqs/dect