Accepting incoming calls on Xiaomi MIUI phones
Xiaomi phones in MIUI firmware have an extended list of permissions compared to an original Android. If additional permissions are disabled, it can cause troubles with incoming calls.
In order to enable additional permissions you need to:
1. Open phone settings
2. Choose point “permissions”
3. Choose subpoint “other permissions”
4. Find the app “Zadarma”
5. Confirm that both permissions are enabled and marked with green checkmarks