iPhone favouring data over wifi

[Willie+C]

Anyone any idea why 2 of the iPhones in my household (14 and 15) continually connect to mobile data in preference to our sky wifi when in the house? It's like they keep dropping from wifi and connecting to data which is totally chewing up the data allowance of n these phones? My other two iPhones in the household (11 pro max and a 12) don't do this at all and always hold their wifi connection in the house. We have fibre max and 2x boosters so it's def not a wifi signal issue!! The WiFi has been reset, there are no faults in my area and wifi assist has been turned off on both of the phones with the issue?

Can anyone tell me what is happening and how to fix it?

[63johnw]

Hi @Willie+C  have you looked at settings, mobile service , then scroll down to WiFi assist to see if that's toggled on. You could try turning it off if so. Also you could turn mobile data off in your phone settings and that will force it to use WiFi.