Todo this go to dialer and dial ##6484##. By doing this you will get options to check components individually. Then check mic and speakers if there is an issue it is better to give the phone for repair. If none of the above steps works, try resetting the phone. Go to settings> Back up and reset > Factory reset.
Iwill buy a XIAOMI Note 3 or maybe the Note 3 pro (with better APN and CPU) ; and i am very happy to discover that there is guys developp rom for theses phones Inviato dal mio Redmi Note 3 utilizzando Tapatalk Click to expand Click to collapse. [GUIDE] MIUI Battery & Multi-tasking Fix v4.1 (Updated) prathameshsd; Apr 14, 2016; 2 3 4
Fix- In rare cases, the message "SIM card not activated" was displayed after the device had been rebooted (02-16) can unlock and possible there is some small subset of people with Redmi Note 3 Pro which somehow get the correct unlock code. Perfectdevil Senior Member. Jun 30, 2012 665 321 Jeddah. Mar 18, 2016 #16 MIUI is alright but I