My iPhone will not work with my grans WiFi

My iPhone will not work with my grans WiFi. We have moved in with her so I’m using up my data. Everything says it’s connected and works for everyone else in the family. My phone is up to date with everything and have tryed restarting everything too. Is there anything I could have switched that shouldn’t be to allow the phone to send and receive messages on this wifi

[Re-Titled by Moderator]