There are three possibilities when the caller is busy:
1. The other party is on the phone.
2. The other party saw the phone and chose to hang up.
3. The other party has set up interference interception, such as setting you to a blacklist or setting your mobile phone to flight mode, which will cause this situation when you call the other party.
The telephone prompt tone has the following prompts:
1. Empty number: Hello! The number you dialed is empty. Please check it before dialing.
2. The called user shuts down: Hello! The number you dialed is turned off.
3. The called user is not in the service area: sorry! The subscriber you dialed cannot be connected temporarily. Please redial later.
4. Caller arrearage shutdown / one-way shutdown: sorry! Your phone is in arrears. Please renew your phone bill. Thank you!
5. Called shutdown: sorry! The number you dialed is down.
6. Network busy: sorry! The subscriber you dialed cannot be connected temporarily. Please redial later.
7. The called user has set incoming call restrictions: Chinese: sorry! The user you dialed has set incoming call restrictions.