The data limit is a useful feature if we do not have an internet flat rate in the contract. After reaching the data limit the mobile data is deactivated by default. We can set our own data limit for this, but the function must be activated first. In the same way, the data limit can also be switched off.

Android 10 (MIUI 12.0)
Step 1:  Open the  Security app
Step 2:  Open the  Settings
Step 3:  Tap on  Data usage
Step 4:  Enable or disable  Data usage
  1. Open the Security app
  2. Open the Settings
  3. Tap on Data usage
  4. Enable or disable Data usage

Xiaomi Instructions