It is important for the users to understand and handle the settings of their smartphones professionally. You can fix your errors without having to go to the repair service center if you know the settings properly. 
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Here are some tips to help you solve your Mi smartphone setting.
(2) Phone numbers saved in your SIM Card
(3) Internet Speed
(4) Downloading
(6) Wave Pay Code
(10) Customizing Status Bar SIM Name
(11) Video Ringtone
(12) Dual Screen
(13) Dual App on Mi Phone
(14) Creating Dual App