If my internet goes down, do I lose my VOIP phone system? How could I ensure my phones will stay up if my internet is down?

Unfortunately, if you run a voip system and rely completely on your own internet connection to run that system, then you are out of luck. There are however, ways to provide extra redundancy so that this never happens. One strategy people are utillizing is keeping one analog lines as an emergency line just in case the internet does go down. This is ideal for the very small business who does not rely heavily on phone calls to conduct business. For larger companies, the easiest way is to get your voip is through a Managed provider. If your internet goes down at your location, a redundant back-up ippbx in your region will kick in automatically and allow you to resume business as if nothing happened. If you were in the middle of a telemarketing session you would never even know it went down. Some Managed services offer a 99.999% up-time guarantee, the highest you can get.