Although Discussion Forum members can update/edit their own callsign, you cannot do this with the VK Logger itself.
This is quite deliberate, to minimise any transient abuse.
For a VK Logger callsign change, please use the "Contact Us" form.
Contact Us > Callsign Change Request
To submit the form, and to prevent SPAM postings, you will need to enter the Confirmation Code.
Apparently, it is not obvious to some users, and they are not seeing it.
The VC code is located right next to the entry box, and will change periodically.
This required to prevent SPAM entries, knowing that a human actually typed in the correct code.
Also, a reminder that profiles that are older than 100 weeks get deleted.
This is done to get rid of stale profiles that are most likely out of date, and/or contain inaccurate information.