I've been getting the 503 failure code when dialing a number in the 703 (Virginia) area code, it started with some regularity later in the week. First saw it Wed, then Thu and on Fri got it a lot. I dial the same number in area code 703 a lot.
My suspicion: I've been seeing intermittent off behaviors in my Obi202 and I'm quite certain they are related to the CallCentric up and down (intermittent connectivity) issues. So, even though the 503 failed call is going out on GV, based on recent observations, my suspicion is CallCentric is the root cause.
Is it a commonality that all people reporting the issue have one or more CC services setup? Also, an important detail to add, I was seeing these intermittent off behaviors in my device even when the CC voice service was disabled, maybe the ITSP profile for CC (where the DNS SRV names are reoslved) was still imposing a latent effect?
Side note: area code 717 in your list Code is in south central PA, not VA,
map. In fact the rate center yo umention is in area code 703