I took off battery and my phone died

Hey guys

yesterday i was using my phone it was working perfectly ! until i took off battery without turning off the phone to change new sim card. since then it died and i putted other battery but still didn't work and i tried to charge it and i tried to boot it with power button and main button and volume button!also tried charge from pc and left it for days without battery i tried everything ''but if you ever notice when ur charger is connected to the electricity and does very light sound bezzzzzzz but when u connect it ur phone that sound disappear which simply means ur phone started to take electricity and my phone is also taking electricity but its completely death

so i need answer what really happen ? no signs no light no vibration completely died, could it be IC power ? or what part should i change ?i live in sweden and the company said will fix it in france and they didn't check it cus its very expansive !

best regards

Thanks.