So I have installed many on-premise Cisco VOIP solutions in the past, but was asked today by a customer who wanted us to host their VOIP in our datacenter since we already host many other applications for them. They currently have an old PXS that really needs replaced, and they could really take advantage of some of the features of Cisco VOIP. They have made it very clear they don't want this on site. They have a large internet circuit and they do have a complete cisco infrastructure with QoS capabilities to ensure VOIP traffic will have priority. The question I have is regarding the phone lines themselves. They currently have a PRI T1 that their phone lines come in on at their location. If I wanted to host their VOIP, I would have to to have all those numbers ported over to a PRI T1 in my datacenter right? Or should the phone lines still remain onsite, but ip phones will just register over the internet?