Hi Albert
All questions should go first to the administrator of the 3CX Phone System who created your accounts. As follows:
- is the PBX at least version V15?
- is the PBX updated with the latest iOS push certificates?
- is my extension configured to receive push calls?
Founded in 2005, when VoIP was an emerging technology, 3CX has gone on to establish itself as a global leader in business communications.