wifi only internet

Solution
For voice though this not going to work, there is reason why you have a data network and a voice network. The 4g data network does not provide enough bandwidth/latency for VOIP to work well, even more so for multiple phones. You can certainly take a router and configure it as a bridge to hookup the phones, but it will not work well at all.
For voice though this not going to work, there is reason why you have a data network and a voice network. The 4g data network does not provide enough bandwidth/latency for VOIP to work well, even more so for multiple phones. You can certainly take a router and configure it as a bridge to hookup the phones, but it will not work well at all.
 
Solution