What’s the best cheap smartphone for a reluctant user?

Ronald rarely uses his Nokia phone, but his grandchildren are pressuring him to get a smartphone. What’s the cheapest good option?I am 72 years old and currently use a non-smart Nokia phone on Asda’s pay-as-you-go network. I put £10 on it a year ago and still have about £3 left, as I only use it for emergencies. My grandkids keep on at me to get a smartphone, but I need one that is unlocked and works with my Asda sim or at least a similar PAYG deal. I already have an Andr