Why can't I access the internet without using Wi-Fi?

[AC Question]

Until two weeks ago I could access the internet from anywhere. Now I need Wi-Fi. I have straight talk with AT&T, my phone is a ZTE Merit Z990G

 

[TechNut79]

Mobile data is turned on? I know, obvious question.

Posted via the Android Central App

 

[Rukbat]

And have you exceeded 5GB this month? After that you get VERY slow internet until the next month (so slow that it seems you have no internet - and what you have is practically unusable).