Just going to additionally toss in (sorry Frankies Girl), although providers like Ting and Consumer Cellular can be a good deal for multi-line households, they're a raw deal for a single line, doubly so at the usage levels you're talking. $10 should be the screaming max you should have to pay per month, and realistically with providers like H2O, you should come in between $4-9/month. Ting's a base minimum of $6/month+tax plus any usage on top of that, Consumer Cellular $10/month+tax plus usage. If you prefer T-Mobile and bucket usage on a single line, US Mobile would be the better option, and still cheaper than Ting.
As for feature phones, again, try to use up and wear out your smartphone since you already bought it, there's nothing saying you can't disable mobile data and use it on the cheaper plans. If you insist on replacing, however, there's really not much choice in feature phones anymore. You pretty much buy what you can find these days, unfortunately.