I am sorry to be the 101th to beat this dead horse (I have no particular beef against pjsip since I have never even used chan_sip), but I feel obligated to report that for a Freepbx 14.1.0.10 install, under
settings / advanced settings / Dialplan and Operational
the comment for the SIP Channel Driver parameter states:
KEYWORD:ASTSIPDRIVER
(…) The chan_pjsip channel driver is considered “experimental” with known issues (…)
what he says 
We just haven’t updated this.
What carrier do you use?? I usually use Vitelity but they don’t support PJSIP. I looked at Twilio and I don’t think they do either. I NEED multiple phones on the same extension, it’s the only reason I upgraded FreePBX
So what provider have you found that works with pjsip? I need multiple phones on same extension asappp 
You can use pjsip on internal extensions, but use chansip for your Sip trunk providers