The mobile clients (iOS, adnroid) should handle the Roaming between different networks. If I change during a call the location from WIFI internal to outside (go out of the company). the mobile phone connect to 3G/4G and lose the active call. It should be possible also otherwhise (3G/4G to WIFI). I made some tests: - Wifi internal only -> Connection to 3CX and communication is possible - 3G/4G only -> Connection to 3CX and communication is possible - Roaming from Wifi to 3G/4G during a active call. -> Communication will be lost - Roaming from 3G/4G to Wifi during a active call. -> Communication will be lost I made also some tests with whatsapp call, skype, and cisco jabber. the other applications/solutions can handle the hopping/roaming. this behavior is common. the customers move during a call through different networks an will be still connected in a active call.