Yes text works, but how will you do that with some old old phone?

1. You can't install new programs; they hardly have an "app store".
2. Texting to a site/office that will hold your wallet and send txs for you would work, but introduces hassle for the payer (typing time) and a host of fees and security concerns.

My assumption is that normal folks would get a smartcard, at least in their family/village while merchants would use a handed down android running my imagined POS app and being connected to a card reader cable.

No banks would be involved and anyone could issue cards as it would be open source - for instance "red cross".
The cycle would be all BTC.