We have attempted to call our own #'s (888-963-4824, 888-453-2187, 888-397-7444 and 888-794-1231) as well as outside lines of 800-472-0391, 800-288-6579, 800-531-8722, and 800-975-6346 and 888-701-8992.
The only thing I have been able to find is a FAQ on another voip service (
https://www.8x8.com/support/using-your-desk-phone/why-cant-i-call-out-to-a-toll-free-1-8xx-number ) stating that dialing from a toll free line to another toll free line may not work due to phone companies not being able to determine who pays for the call, but I figured they would just always bill the recipient, and we have been able to make calls in the past.
There are also no errors in our phone logs either at the time the calls are placed. Thanks!