app store asks to use cellular data when on wifi

When I try and download new apps or update my current apps from the app store, I am shown the size of the download and asked if I want to use cellular data or download later on wi-fi even though I am on my home wi-fi network. If I click continue it downloads fine, even if I have cellular data turned off. I have restarted my phone, turned off and then back on my wi-fi, done speed tests to check the connection (with 800+ mbps), and still get the message.