Am I using mobile data when connected to wifi?

[Chanice]

I just got a samsung galaxy s3 and was wondering, If I am connected to my wifi at home or at school then do I need to turn off my mobile data even though I am connected to wifi and will it charge me or should the wifi take over and my mobile data only connect if there is no wifi? Also is it ok for me to use whatsapp, vine, instagram and twitter when only connected to my mobile data? I get 1GB a month. I just want to know what I should and shouldn't do when it comes to the internet on my phone.

[Ash]

If you are on wifi, it should not use mobile data. You can turn off your mobile data if you want to be safe, but it shouldn't.

Those apps seem ok to use with a 1GB plan. Stay away from streaming movies and even youtube if you don't want to risk going over.

[ScσττRΛSC³]

Phones use 1 or the other, not both.

Try to use wifi wherever possible.

[Gareth]

Nope