Hi, I have recently got meself a Digi internet phone package for like 3gb per month for so and so. Do i have to set my Sony Ericsson Xperia Arc to National Roaming?

sorry for noob question,
i wasn't being able to get the internet browser on my phone working or the Play Store working for the last few days even though apps such as facebook or whatsapps work perfectly fine.

only after i set my Roaming option in the mobile and network, to National Roaming can anything start working.

im not sure if my internet setting is correct

thanks in advance.