Existing customers pay $80.00 for the same thing (or far less) as new ones pay $35.00 for?

I live in an historic neighborhood; there is fiber to the box at the end of my block, and copper the rest of the way to my house.  ATT is pushing VERY hard for us to switch to fiber.  I would have switched a while back (of course!), if I had a half day to sit home so they could install it.  I just haven't had the time or freedom to skip work.  (Of course, I'm also thinking it's a certainty they will raise the price a LOT once we are all on fiber, if not sooner.  They always do.)

For a few years now, I've paid $80.00/month for broadband speeds "up to" 45Mbps.  Speed tests show that at some random off-peak times I do have that POTENTIAL capability.  However, during the week, I have Zoom calls drop frequently--during business hours, usually.  These calls use 1.5 to 1.8 Mbps maximum, yet they won't stay connected even when NOTHING ELSE in the house is using bandwidth.  I've done all the speed checks, router troubleshooting, etc. already.

This built-in limit is partly why, although I am also paying for a MONTHLY data allowance of 1536 GB, I have never used more than 330 GB/month.  I'd need 4-5 months to use that much at full speed.  At speeds sometimes apparently (at least intermittently for hours at a time) as low as1.8Mbps, it would take years!

I am paying for unreliable "broadband" which can't sustain a Zoom call at busy times, and would never make it possible to use the 1536 GB allowance they added to my plan.  I'm reading on other sites that the Internet traffic management system (PPS) functions the way throttling does.  This is by making unimportant users' access low priority, leaving room for businesses to use unlimited amounts. (Data limits and throttling are forbidden filthy words at AT&T, they say.)

It seems they are making my neighborhood a low-priority connection, which causes at some moments near-zero bandwidth for my house.  That's just long enough to make a Zoom call crash.  Is it coincidence that it started not long after the "switch to fiber!" letters arrived?  Common sense suggests that question, at least.

When I complain about the connection, they jump right over my questions and this math and push fiber installation.  This is obviously the back-up sales plan after the letters haven't worked.  AT&T is a megalith that ultimately will do whatever it takes to win; it seems practical just to cave in. Or switch service providers.

However!  They "promise not to change my monthly cost" and brag about the basic fiber plan of 300Mbps.  Meanwhile, they charge new customers (if they bundle wireless as I already do) just $35.00/month for the same 300Mbps, with a $100.00 gift card, while just $60.00/month would get me 1 GIGS download speed if I were a new customer AND a 150.00 gift card!  I am paying 80.00 for 45Mbps I am not actually getting when it matters most.

Let's see:  I am paying for at least 5 times the data allowance I can ever use, and $80.00/month for 45Mbps download speeds but can't count on a 1.5Mbps Zoom call to stay connected....And AT&T wants me to be grateful for being pushed to upgrade that they are willing to give me the slowest fiber they have for 2.5 times the rate new customers get?

REALLY!!!!  Can anyone explain how this is anything but coercion (throttling) and punishment for being loyal to AT&T but slow to upgrade?  Would you switch ISPs, rather than accept whatever AT&T wants to throw at us?