Here is the USA tou can Google:
Cheap Cell Phone Plans
And find lots of new and old firms that claim they can do it.
Myself, I have not DONE very well with cheap phone plans.
But I am still trying.

So my question is this:
Do you have a good cheap plan you found in your area?

I saw one that says you can pay as little as $3 a month if you already have a phone.
Well, if it too good to be true, it is too good to be true.

BTW, CONSUMER Cellular is good, but it is not under $20 today.
Here in Britain, if you own a phone yourself, you can get what are called 'SIM-only' contracts. You pay monthly for voice and data and text service. My contract with VIRGIN Mobile costs 13 pounds, (17 US dollars) each month, and for that I get 2 GB data, 2500 call minutes, and unlimited text messages. In Europe we don't pay for incoming calls or texts. If I don't use all of the data it rolls over to the next month. My contract is a 'rolling 30-day' one, that is, I can terminate with 30 days' notice.republicwireless.com offers $20 / month service that gives you unlimited talk & text and 1GB data. You can BUY a phone from them OR you can bring your own phone.
If you have your own phone, you go here to see if it's compatible with their service: https://republicwireless.com/pages/compatible-phones.

I currently subscribe to this plan and it's decent for me.