As above really.
I've said DD can have a phone in year 6 for safety as we want her to start getting used to walking on her own (plan is to start with her walking to the car outside the school just out the gate and down the road for about 1-2 minutes and then build up to further distances) in preparation for secondary school.
What type of phone do your children have? I'm definitely not looking at anything top of the range, I've had a look with my provider and can see an IPhone 11 for £20 a month. Just need something half decent so I can use find my iPhone or similar to see where she is, and for her to be able to use it in an emergency if needed so something with decent battery life?