Unhappy GT-I9505 3G not working after 4.4.2 update

Guys can you please help me? I got a strange problem. After updating to Android 4.4.2 KitKat(Official Samsung update) my phone can no longer connect under WCDMA only. All i can get is 2G and I know the coverage of the mobile operator isn't the problem. I tried even some custom ROM's but still the same. When i switch to WCDMA only the phone can't connect at all. Things i tried so far:

- Different official Samsung ROM's
- Custom ROM's
- Hard Reset many times
- Clean cache
- Rooting the phone
- Flashing a different modem

And as far as I know now i can't go back to older android because of this stupid bootloader lock... Do you guys got any idea? What more can i try to make it work? Thank you.