Can't access internet through the ATT data plan on my Nokia Lumia 635

Hi, I've had a Nokia Lumia for a while now, and haven't been able to figure out how to get Picture messaging or internet working through my data plan. I've tried a handful of different APN settings and haven't gotten any of them working.

But I really need to be able to access the internet on the go as of recently.
Any help would be nice.