When adding multiple customer contacts to Yealink devices, xml format should be as the following:
<YealinkIPPhoneDirectory> <DirectoryEntry> <Name>Contact 1</Name> <Telephone>Phone Number 1</Telephone> </DirectoryEntry> <DirectoryEntry> <Name>Contact 2</Name> <Telephone>Phone Number 2</Telephone> </DirectoryEntry> <DirectoryEntry> <Name>Contact 3</Name> <Telephone>Phone Number 3</Telephone> </DirectoryEntry> </YealinkIPPhoneDirectory>