Streaming Audio with WIFI and Screen Locked

[Ad Guy]

I've googled this and got alot of information, but really no good answer.

I have an Iphone 4 with all the current IOS 5 updates. When I sleep at night I like to listen with headphones to streaming audio either through the Apple Podcast app or the Iheart Radio app. I plug my phone into the wall charger every night so it is running on A/C power. I am connected through my WIFI when I start listening and then I activate the lock screen to make the screen go black.

The issue I am having is that my cellular data use has been growing much faster than I can account for and is much higher than before.

My question is with the power cord attached and me streaming audio is my phone switching from wifi to 3g once the lock screen is activated? I know that without A/C power it is supposed to, but I thought that if the power cord is attached the phone would stay on wifi even when the lock screen is activated. Especially if I am streaming audio at the time.

I think my high data usage might be from the wifi switching to 3g once I activate the lock screen.

Any thoughts? Thanks

 

[speckledove]

When I lock my Iphone 4 - it uses cell data, I am not sure why and I would like to turn that off, but I learned that through my husband and my data usage confirmed it as well. I would love to know if there is a setting that would turn that off.

Thanks!
Speck