On your request for BYOD settings on the HT502, this is what I am using after tweeking to resolve several issues. These are changes from default.

I'm using the HT502 in a static IP mode, behind a router. My router does not require port forwarding, however some may require forwarding 5000-65000 UDP. In the dial plan, replace the 609 with your local area code. This plan works with 7, 10 and 11 digit numbers.

NAT Traversal (STUN): No, but send keep-alive
Outgoing Call without Registration: No
Register Expiration: 4 (in minutes)
Use random port: Yes
Check SIP User ID for incoming INVITE: Yes
Allow Incoming SIP Messages
from SIP Proxy Only: Yes
Preferred DTMF method:
(in listed order) Priority 1: RFC2833
Priority 2: In-audio
Priority 3: In-audio
Dial Plan: { *x+|[49]11|123|<=1>[2-9]xxxxxxxxx+|<=1609>[2-9]xxxxxx+|1[2-9]xx[2-9]xxxxxx}
Gain: TX -4dB RX -4dB

I'm not a master of VoIP, so this should not be taken as the most optimal configuration, but it works for me. I welcome any suggestions for changes.