AT&T Wirelesss Have smart phone with unlimited data plan since 2009 & AT&T will not honor unlimited data plan with upgrade. Internet, Internet

I have two smart phones with what I thought was unlimited data plans. AT&T no longer offers unlimited data plans. When I upgrade phones, I wanted to keep the unlimited data plans since I already have them on these two phones. AT&T says I only have one smart phone, not two. I have had both phones for over two years. AT&T says I don't have two smart phones. I told them I do have two smart phones, but they refuse to acknowledge this, so that they won't have to let me keep both unlimited data plans. They want to charge me for some new tiered data plan that I have to pay more money for.
I have asked them to correct this mistake, which they made 2 years ago and switch the Unlimited Data Plan to the Smart Phone Unlimited Data Plan, which would allow both lines to have unlimited data plans when I upgrade. I wish there was some way to make AT&T correct their mistake and honor the commitment that was made back in 2009. I have been forced to honor my part of the commitment.
 
I have been a loyal customer of AT&T over 10 years.
It is apparent that AT&T does not care about their customers, honor their commitments, and that they are not a company with integrity.  I will be switching wireless providers.
 
Sincerely,