Several months ago I purchased a Verizon 'black box' in order to switch to them as my land phone carrier. I continually had difficulty with phone numbers getting through with the message, "Your number cannot be connected as dialed".
Clients and friends complained that my voice always sounded 'tinny' and could barely be heard.
Three times I sought Verizon assistance with the problems - once in the store where the box was purchased; twice via the phone. Finally I switched back to AT&T in order to protect my client reputation and was charged a $160 fee by Verizon for early termination although the problem was their equipment.