So what? Should I assume that my battery is broken/ weared off in some way? Phone was working for few days and turned off beeing connected to wall charger. Still the device without sim card runs 2 days without charging and under heavy use. No battery problems, no any other issues involving battery.

Please guys stop guessing. How is that even possible to kill battery voltage when connecting to gsm network?

Please continue with me as we do. I will buy new battery if you can provide me with good supplier.

And I can only assume that my spent money = wasted money.