Insane power drain and data usage

Hello people.

And yes, i'm having both of those problems. This evening around 17:00 i fully charged my 3GS, switched on cellular data but not the 3G and put the phone away. And while the phone is near a speaker, i constantly hear that sound it makes when you make or get phone calls. Meaning it's using the internet ALL the time, cause the noise just doesn't stop.

Anyway, after about 15 mins, i checked the phone for usage stats. And it already had 2 megabytes of incoming data. The received data was 57.1 megabytes at first, and 59.6 in 15 mins. Then i put the phone away again, didn't touch it for another 6 hours. After 6 hours, it's battery was dead. Plugged in and it's now charging at the moment. And another weird thing is, the received data usage is back to 57.1.

Push is turned off.
Fetching mails are off and set to manual.
Notifications are off.
0 applications running in background.
Just to be sure, i closed all safari pages before closing safari. Also cleared all cache and stuff.

ANY idea or some kind of help would be much appreciated.

PS. forgot to write, i'm from Turkey, using an unlocked and JBed iphone 3GS that was bought from US.

 

I made a hard reset to have the phone clean. Didn't have problems until i started installing apps. After a few installations the phone and data usage started increasing again while in sleep. Then i deleted all the apps one by one, checking if the problem is gone after every erase. No luck. Now i have 0 apps at all, and still something going on in the background while in sleep (and of course there's no apps running in the multitask window). Still don't even have any mail accounts set up, so i'm sure it's not a problem with push or fetch. And when i just turn off the cellular data in the settings, phone usage also stops along with the data usage.

I'm just going crazy feeling really hopeless.