I'm guessing you're referring to a VoIP phone? I'd advice checking to make sure you have a quality net connection. This doesn't necessarily mean a fast connection. You can try using
myspeed.visualware.com, which will help determine if your net connection, I take it's mobile data, is suitable for VoIP.
Note that if you're interested in Verizon's standalone mobile data home phone connect with unlimited minutes for $20. month, Walmart has the exact same setup with Straight Talk Wireless Home Phone for $15. month. You have to buy the 4G VoIP router/PSN, but also uses Verizon.
Personally, I use the MagicJack Plus and also forward my cell phone number(Google Voice) to it as my Verizon wireless has 0-1 bar signal from my home. Doesn't use any Verizon minutes. Also have a Obihai PSN adapter which connects to a home phone and allows incoming/outgoing calls using a Google Voice number for calls in the U.S./Canada at no cost.