Why is my phone not working correctly?

[AC Question]

A few weeks ago, I stopped using my school's WiFi as it basically hinders my phone from doing anything. My phone would sometimes get blocked from working and it was frustrating but for the most part, it would still work fine just a lot slower. Then last week, my phone stopped getting messages. I could send them all I wanted but I wouldn't receive any back. I did everything to try to work out the problem and I even factory reset my phone. Still, no messages were received. What I did notice though was that every time I got to my school, my phone would magically receive all the texts I didn't get after I got home from the day before. I feel as if my school's block has damaged my phone because I've tried about everything (soft reboot, hard reboot, factory reset, other messaging applications, turned off auto-retrieve, and a few other things). I really need help as this is frustrating having a phone that doesn't work when I need it to. Sometimes I call people and they don't receive my calls. So it's worrying me that I have a phone that is basically unusable. Any help is appreciated. Thanks!