China
China has strict telecom regulations that impose specific requirements on international call traffic entering the country. FlyNumber users with traffic to China should understand these guidelines to avoid service disruptions.
Key Terms​
- A number: The caller's phone number (the originating party)
- B number: The destination phone number being called
- CLI (Caller Line Identification): The caller ID displayed to the receiving party
- E.164 format: The international standard for phone numbers (e.g., +14155551234)
Traffic Restrictions​
The following call patterns are flagged by Chinese telecom authorities and may result in blocked calls:
| Restriction | What It Means |
|---|---|
| No repeat A number calls | The same caller cannot make repeated calls in rapid succession |
| Valid A number required | The caller's number must be in proper E.164 international format |
| No random B number calling | Calls cannot be placed to random or sequential phone numbers |
| No China-to-China routing | Calls originating from within China cannot route through FlyNumber to China |
| CLI must be authentic | The caller ID must display the actual originating number without modification |
China requires that the Caller Line Identification (CLI) displays the true originating number. Calls with blocked, anonymous, spoofed, or invalid caller IDs will likely fail. If you're forwarding to a phone number, be aware that anonymous or blocked callers may not be able to reach your China FlyNumber.
Automatic Blocking Triggers​
Chinese carriers monitor traffic patterns and may automatically block numbers exhibiting suspicious behavior:
- High volume of calls to unallocated numbers: A pattern suggesting machine-generated or automated dialing
- High disconnect rate: An unusual number of calls where the called party hangs up immediately, which may indicate unwanted or spam calls
Service Limitations​
- No SLA available: Due to the regulatory environment in China, service level agreements are not available and services may be disconnected at any time without notice
- Calling card services prohibited: China FlyNumbers cannot be used for calling card or callback services
Error Messages​
If your call traffic triggers any of the above restrictions, you may see an "Internal Server Error" status in your FlyNumber call history. This typically indicates that the call was rejected by Chinese carriers due to a policy violation.
Recommendations​
Best Practices for China Traffic
- Ensure valid caller IDs: Make sure callers have properly formatted, non-blocked numbers
- Avoid high-frequency calling: Space out calls from the same originating number
- Monitor your call logs: Regularly check your call history for failed calls
- Consider VoIP forwarding: VoIP configurations may provide more flexibility for handling various caller ID scenarios