1. The first and most common reason is that the caller ID function has not been started. This function is included in the phone package, and it needs to be opened separately if it is not included in the package.
2. It may also be that the number location is not updated in time. In this case, you can try to reset the number location first.
3. By using network software, the caller encrypts his phone number and hides his phone number mobile phone "Unknown" or "Private Number" will be displayed on the.
4. Callers have opened the calling number hiding service at the operator, so that when dialing a number, they will not display their phone number or reveal their identity. This service will only be open to people in special industries.
5. Some mobile phones can also hide their numbers when making calls through settings.
6. This can also happen if the caller is abroad, because the information of operators in different countries is incompatible, resulting in incomplete transmission of information.
