The tips needs Net Monitor enabled. Be aware that the trick will remove Netmonitor in some sw versions like v4.73 and v5.04.
Launch the Net Monitor in your Nokia 51xx / 61xx
Execute the test number 497
Free calling for about 90 sec should now have been activated.
Launch the Net Monitor in your Nokia 51xx / 61xx
Execute the test number 497
Free calling for about 90 sec should now have been activated.