Grandstream Phones have the possibility to add a phonebook.XML file. For this feature please consider the Following:
For an Example of the XML file access here.
Download the file and Each Line represents a record for the Phone book so add as many as you need.
Then just replace the values for:
After the file is ready upload it to your server and provide the appropriate url for nexogy to setup the respective parameters each phone must then be power cycled in order to get the new configuration.
You need to know if the feature is available for your device, not all Grandstream devices support this feature.