Bait & Switch on wireless plan / billing

Up until mid July 2022 I had the grandfathered 30gig data plan with unlimited call/text. My wife was going over data multiple times and or July I was looking at additional $100+ on top of my monthly bill of $250. So I thought I would call to find out how much would unlimited plan cost. Rep told me that it will be cheaper and that I should add another line (I had 9 lines now have total of 10 lines) to get even more discounts. I was excited and asked AT&T rep on call to email me the breakdown of monthly estimates.  I was amazed to see that after discounts (paperless/autopay and my company discount) I would pay $22.50 + tax/fees per line for unlimited plan and with additional line to spare for future.  So in short total for 10 lines would be $225 + taxes/fees.  Which would have landed me in $250-$270 per month which I was fine.  However, two months into the unlimited plan I saw the bill and it turns out that my corporate discount was not applied.  I called AT&T customer service and they said since I was on basic unlimited plan I do not qualify for my corporate discount. I told them had I known this I would have not switched to unlimited plan as additional $100 per month is a lot ($350 instead of $250).  I told them rep had sent me an rate email (attached image) based on which I made decision to let go my 30gig plan.

This is a huge disappointment and I really feel that I was cheated by AT&T.  I have been their customer for 20+ years (since Cingular days) and totally feel that my loyalty has no value. So I'm going to be looking for some other carrier who can offer me better rates.