Beastmobile.net has an unlimited talk and text for $4. That plan is only for Sprint phones. Higher priced plan also works on ATT phones.
You can also get a free Sprint Alcatel flip phone with their $24 plan. Doesn't seem like there's any minimum amount of months needed. Pretty good deal just for that. One eBay they're ~$45
Saw on SD that it doesn't look like they have an option to port out a number so don't port in any.
Obviously same warning as always, don't rely that this will last.