How to obtain an Arris BGW210-700 modem?

I recently had fiber installed and am happy to be back with Uverse TV after a brief interlude with Spectrum TV service that just isn't as good or as user-friendly.  (I moved and ATT is just now available at my new location, so Spectrum filled the gap for a couple of months).

I need to obtain an Arris BGW210-700 router, because it's configurable to disable SIP ALG (for VOIP) and the Pace 5268AC I was provided is not, and understand these are the only two modems ATT has that are compatible with fiber Internet service.  I called the local techs supervisor and she hasn't seen a BGW lately - says she gets what she gets, no control.  She suggested calling in to order one.  First attempt, promised delivery last Saturday (next day) no problem.  Didn't happen, called on Monday no record of any such order despite being given a confirmation number on Friday.  Was told an Arris modem would be "requested" but is not guaranteed (warehouse can't ship what's not there) (second attempt).  Today, I receive a notification that another 5268AC has shipped to me.  Not sure what I am supposed to do with that.

Any ideas on how to obtain my preferred modem, the Arris, instead of the (current/local) default Pace modem?

I understand from these forums the Arris is actually the updated / newer modem, so perhaps if I try again in a month or two it will be "in stock" and the Pace's will be "out of stock"?  Would obviously prefer it sooner, as the modem is interfering with my third-party VOIP service.