If your Mi account is unrecoverable for any reason and the phone becomes locked there are two ways to solve the issue: 


Solution 1

https://account.xiaomi.com/pass/retrieve/apply?type=pwd&;externalId= 


e.g. https://account.xiaomi.com/pass/retrieve/apply?type=pwd&;externalId=1234567890


Add your MI account number at the end part after externalId= Xiaomi company will deal with your issue within 2 working days. Please note the process is verified manually so in some cases may take a little bit longer to fully be resolved.


Solution 2

Open the following page https://account.xiaomi.com/ then fill in your MI account details, select the forget password option and follow the instructions to get help and support from Xiaomi Mi Customer Support Team.