Should a SIM Card and Cell Phone Produce an Author

Question

I am trying to use FreePBX 13 (a GUI version of Asterisk) to create a mock VoLTE network with our cellphones (an iPhone 6S+ and an LG G3 VS985).

FreePBX has been set up as such: FreePBXForums: Using FreePBX 13 with a Mock Cellular Network

At the moment, we are able to register and make calls with computer clients, but the UEs (aka the cellphones) fail to register because of a "realm" mismatch among other things. Because of this I have a couple questions:

1. If a client (even a UE) recieves a 401 Unauthorized message, is it allowed to stay static as what is happening with the UEs, or is it supposed to modify itself regardless?
2. If it is allowed to stay static, is there any way to modify the in-congruent authentication parameters on either side?

If you would like to see the packets themselves, please see entries 23 and 16 (respectively for UE and Client registration) from the forum linked above.

Please let me know if you have any questions. I am somewhat new to SIP, so that is why I am asking this question.