When making calls between the VoIP and ISDN worlds, the phone number is displayed, but not the name (display entry). When the technology at the transition between VoIP and ISDN (gateway) is renewed in August 2023, features such as the transmission of the name will no longer be available due to incompatibilities in the transmission protocol. At present, it is not possible to say whether there will be another solution for this.
The cause is the outdated (20 years) ISDN telephone technology.