You cannot do this yourself. That only works when you are in the Netherlands, connected to the KPN network.

Put the phonenummer (06xxxxxxxx) and the simcardnumber in your forumprofile. Use the field "Persoonlijke opmerkingen” (only visible for you and KPN) and save your input by pressing “Sla wijzigingen op” at the bottom of the page.

Report back here when you have done this, then a moderator can activate it for you.

Hi @Coriolanus ,

Were you able to put the phonenummer and the simcardnumber in your forumprofile ?
Then I can alert the moderators.

The profile is still empty, so hopefully @Coriolanus has found the solution elsewhere. 

Thanks for the help @RBxx!