I've been on the typical annual cell phone plans with Tmobile and then Verizon now for over a decade, so have not really been paying attention to "pay as you go" options. I have some relatives who live outside of the US, but will be spending 1-2 months at a time in the US over the next few years. It would thus not make sense for them to maintain a monthly or even annual contract with a provider. Are there still any viable "pay as you go" options that might be good options for them?
I know in the UK, Australia, and parts of South East Asia, you can purchase SIM cards that come loaded with $x of credit (and/or data). They also come with predetermined phone numbers. The numbers and credit expire after x months of activation, unless you reload or top the account up with more credit.
Is there anything similar in the US?
How do they work exactly, though? At least from what I've been able to see on their website, Verizon's 'prepaid' service is a monthly service, which is not what will work for them. They need something where they can just pay up front and use it until it's exhausted, without having to worry about recurring charges each month.
You want something like TracFone 400 minutes for $100 to use over 365 days -- $8.33 per month. There are many options you have. Try looking at the cell phone page on Walmart.com - lots of options to look at there.