How am I using data without a data plan?

I have a iPhone 5s with tmobile pay as you go and to my last message I can't reply to it so I'm making a new one my data per app is 500mb

Go to Settings --> Cellular. Then scroll down to the list of apps. The list should tell you how much data each app is using.

Read this: http://9to5mac.com/...ata-usage/

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Then you could make data plan

I coulnt it kept saying my post was deleted