iPhone XR showing 4G and WIFI internet connection but apps will not work

My Daughters IPhone XR is showing internet connection via wifi and cellular but the Apps and internet will not connect. I’ve tested with different Wifi and it still won’t connect. I can still make calls via the phone. I believe this is through the cellular network. Telstra is the network provider. Is there a fix that I can do that won’t result in a full reset. I haven’t backed up the phone in a few months.