I agree with @chrischevy ; I don’t have a warm and fuzzy feeling about VoIP.ms. Termination is stellar, with servers in many cities and AFAIK they have never had a systemwide outage. But for most small businesses, origination reliability is paramount and VoIP.ms does not have a robust architecture – at any one time, a DID is tied to a specific server. If it’s down, incoming calls fail and in some circumstances the caller will hear the dreaded “disconnected or no longer in service” error announcement.
Up until a few years ago they had a bad reputation for reliability. They “fixed” the problem by moving the servers to better data centers with redundant internet connections, SSD RAID storage, proper UPS / generators / redundant power feeds, etc. But server hardware and software can still fail, and when that happens you don’t get calls until either their engineer reroutes the affected DIDs, or you log into their portal and do the same.
Also, they are not a carrier, so the support problems dealing with a middleman are inherent.
On the positive side, the service includes basic PBX features at no extra cost. Very small businesses may not need a PBX at all; for those VoIP.ms can be a good value. But for us here who are buying dumb pipes, it’s not.