How to unlock phone that has been disabled but not signed into iCloud?

I allowed my daughter to keep my old iPhone 6s. It was signed into my iCloud but she would keep ignoring my calls while she played on it so I signed out to avoid any other missed calls. I have a passcode on it so I can monitor when she uses the phone, well she took it to her dads over the weekend and ended up disabling the phone and it says to connect to iTunes. I’ve done that but since it’s not signed into an account it can’t help me. I’ve also tried calling support and they just told me to use a different pc, which I don’t have. Does anyone know how I can factory reset or help me out. I don’t want to see a perfectly useable phone go to waste, Thank you.