Just a word of advise from my own situation. In digi, if you are using prepaid mobile, you will be charge RM10 for 1MB. I used it once for emergency and the bill came up to RM90 for 9MB. Not that I am blaming them but just be careful of the spending because it costs a lot.

I not too sure for other operator and postpaid, but for DIGI prepaid, just leave the APN in the cellular data network blank then it wont use edge, Only will connect to wifi when available.

But when you need to use the mobile internet, just type in the APN diginet and that will use the mobile internet by Digi.