I have a customer (school) that needs to call from a home telephone or mobile into the 3CX system and change the digital receptionist. This is a critical need because snow and fog requires the administrators to change a message to advise parents and staff of late starts or class/school cancellations. The uses do not want a 3cx extension on their personal mobile phones. They do not have broadband so I cannot provide a remote extension. Is there a way I can accomplish this?