Wifi ( I think?) Help!

So! I keep getting blocked sites on websites I can use on wifi just fine, it’s only blocked on data. Like content filtering warnings I get on sites I use on wifi daily, and it’s not just on one browser? It also says talk to your system administrator, but I’m on my own device. A) how can I solve this problem? B) what is this problem and why does it happen? I’ve had this problem for about 5 months now, and it’s really getting on my nerves.