AT&T's Unlimited plan for 1 line costs $40 per month.
It rides on the AT&T network for coverage.
It includes unlimited minutes, unlimited texts, and unlimited high-speed data per month. You get 10GB, then 128Kbps of hotspot data. Video streams at 480p quality.
The AT&T Age 55+ plan has deprioritized data. Having deprioritized data means you may temporarily experience slower speeds during times when the cellular network is busy. You'll resume getting the fastest speeds available when the network is no longer busy.
Taxes and fees are extra on this plan. I estimate they will add another $6.06 to the price. Your total montly bill will be about $46.06 per month.
Overall, I recommend the AT&T Age 55+ plan because it is a good value.
You can also check out these plans with the same coverage and data amount (scroll left and right to browse plans):