SIP Troubleshooting - Wrong Caller ID for Incoming Calls

The caller ID is piece of information that will be passed from telco to telco when a call is placed. Each telco can have different caller ID format and, as calls may go through several networks before reaching us, the information may be altered along the way.

There are three situations that can cause failure to show intended caller ID:

  • The originating telco may not send the correct format or the original From number.
  • A caller ID may be modified along the way by any intermediary telcos
  • The caller ID may be lost or replaced* when crossing international borders

When we receive an incoming call, we perform basic normalization to E.164 formatting. Otherwise, we will pass along the information exactly as we receive to your application. It is currently not possible to discover the origin caller ID once it has been altered by telcos.

Example: Singapore Resident using Singtel mobile to call our Hong Kong Number.

You will not receive Singapore mobile CLI as the CLI will be replaced by other CLI (ie a random local number) according Hong Kong CLI regulatory. The CLI will be replaced by the 1st HK terminated operator. 

Singapore Number > Dial HK number > (1st) HK operator replaces Singapore CLI according to HK CLI regulatory > CLI by regulatory > Customer side.


According HK CLI regulatory, CLI for HK mobile only, There are no CLI allowed on the HK Landline.

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