The phone doesn’t explicitly say whether its using volte or not during a call, so I did some searching and found that dialer code. The phone says it does and the 4a is new enough, so there isn’t any reason to believe otherwise.
This wasn’t addressed to me, so just my two cents: Samsung is just as bad as google. I’ve seen blocklists for ad- and telemetry-blocking that are samsung-specific, which means they’re at least bad enough to warrant the effort to make a samsung-specific blocklist.
One last thing: this PIN is something the carrier gives you to carrier-unlock your phone, and at some point you’ll have to enter it in yourself. Its been a while since I’ve done it and I seem to recall the details varying a bit from carrier to carrier. I’m not clear on if you’re currently using red pocket or if you’re switching to them, but calling whomever you use and asking for your unlock pin should get you what you need.