Such systems are possess and employed by the company in lieu of a telephone corporation. the phone can only be the supplier or service supplier of these solutions.
FXO gateway: FXO gateways are an acceptable Resolution https://neiltcbe682160.blogdun.com/31108084/ip-pbx-dubai-voip-pbx-pbx-supplier-in-dubai-ip-pbx-system-dubai-can-be-fun-for-anyone