1. Received call without activating SIM card
Dual SIM card settings
Dual SIM call forwarding (ON)
2. Read your SIM card serial without remove it
3. Rename your SIM card
Even your mobile have only 2 slots. But, you can change (rename) them to 4 or 6 ...
4. Developer Options
Don't keep activities: Destroy every activity as soon as the user leaves it
5. Enable "Third Hidden Battery Power"
Imagine your cell battery is very low . To activate, press the keys *3370# . Your cell phone will restart with this reserve.
6. Record with the best Quality
7. Know your battery version