Can at&t disable Wi-Fi connection to my iphone 6?

So i used to use home hi speed Wi-Fi on my iphone 6 when i first got it then i connected it with at&t, since then i can't use Wi-Fi on my phone not even McDonald's Wi-Fi works, it connects to Wi-Fi but doesn't work. Well this week i was 2 days behind my at&t bill so they took out my service and like magic my Wi-Fi started working, later that day i payed my bill and once my service came back the Wi-Fi stoped working so wth is at&t doing something to my phone? I only have 2 gs of data so once it runs out i'm stuck with no Wi-Fi, i think there doing something to my phone in hopes i add data to my plan

I believe you are exactly correct. AT&T is in business to make all the money possible.
You might try a different phone service.
Al