Grandstream phone not updating time
You must restore the phone to factory default (restore Vo IP Settings) to reset the "Account Name" field.
The WWW interface will allow you to change the field, but the phone will not accept the changes without the reset. Navigate to the Dog-Eared page-turn in the upper right of your browser, then select "Reboot".
Each user has a set of credentials which will be needed to configure each phone.
For each phone that you are configuring, obtain the following: You can find this information in the user detail pages under the "Users" tab in the "Phone Configuration" section.
You will want to use the IP address information given in the link above.