cellular radio - My phone is not connecting to the cell network (No Service)

I have an Android KitKat based phone. For over a week the phone is getting poor (at times) or no reception but the WiFi and bluetooth is working.

There is a cross near where the range is shown and I get "No Service" in the notification. This screenshot summarizes my situation:

Here is a list of things I tried to do, but did not solve the problem:

1. Get a new duplicate sim card.


2. Use a working SIM card from a different service provider.


3. Switch to 2G mode and back.



4. Reset my phone.


5. Completely flash the stock ROM again.


6. Flash several modems from XDA.

Edit: Even if it is a hardware issue, is it possible to get some debug information? Like for example, somewhere in the kernel logs, it should be possible to know for sure what is happening, right? What and were to look for this information?

Edit2: Device is Lenovo P780, ROW (not chinese) per OP clarification