App not downloaded on phone but using phone data/wifi

My daughter's phone has suddenly started using wifi and data, an outrageous amount, on an app that she has not even download. Since midnight, it shows on her screen time that she has used over 8 hours (it is 11 am right now). The same with safari, she never uses safari but it shows the same amount of time used, and between Sunday to Tuesday afternoon, it showed over 31 hours used on safari. She looked in her app list to remove the mystery app but it's not there. She also searched the phone to see if it is hidden, but the app is not anywhere to be found. I am concerned for a large cell phone bill, as well as what is being accessed on her phone. HELP!