IPhone 4s with AT&T can't access certain apps on cellular data?

I have an iPhone 4s on AT&T, about 2 years old, and just this last week I have lost the ability to connect to facebook, snapchat, and some other apps when I'm on my cellular data. Safari and google app still work on cellular data, but some other problems exist, such as that my recent calls have not been updated since the problem started. I've reset network settings and tried a few other little things in the settings app based on advice online, but nothing has resolved the issue. Also, recently I downloaded a gameboy emulator on my phone without jailbreaking it, and I don't know if this has affected it in any way. Apple then disabled the emulator on the 16th of July (I think), but I was able to restore it without any problems by turning off my automatic date/time check and setting the time back a few weeks, since the "signature" the app was using was still relevant before that time (as you can tell I'm not a real techy, I read this online as well).
Thanks!

Added (1). Samantha. I guess I should have also mentioned this. I took it to my local AT&T store and the salesman said that there was nothing they could do, but that if I took it to an Apple store they would be able to shutdown and restart my apple account, which has fixed some people's phones with (I guess) similar problems. He sort of suggested that the issue might be that I'm logged in to my itunes on a foreign device, but I know for a fact that I haven't logged in anywhere but my own laptop in the last few weeks

I would take it into the closest AT&T store (not the apple store) and get their opinion. They won't charge you for asking). And usually it can mean that your sim card is just burned out and then they would replace it for free.

I don't think the emulator did it just because that's a 3rd party app and shouldn't have any affect on your DATA from your phone company.