Before you spend a dollar on a device, answer this one question honestly: does your 8 year old regularly go places without an adult?
If the answer is no — they are dropped at school, picked up from school, and mostly at home or supervised in between — then your child does not need a mobile phone. They need a home phone. Something they can use to call you from the house, from a friend's place (on that family's WiFi), or from wherever they are based. A WiFi home phone covers this completely, with no SIM, no plan, no risk.
If the answer is yes — they walk home, catch a bus, stay home alone after school — then a basic dumb phone for outside-the-home calling becomes worth considering alongside the WiFi home phone. But you still do not need a smartphone. Not at eight.
The phone industry profits from parents conflating "my child needs a safety device" with "my child needs a smartphone." These are not the same thing, and at age 8, the gap between them is enormous.
