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Knowledge document #28

Cannot make outgoing calls over the internet

You can't make outgoing calls? The telephone does not work or the telephone number is not registered? ✔ Here's what to do.

Outgoing calls cannot be made over the internet with a FRITZ!Fon registered with the FRITZ!Box. The problem either occurs sporadically or all the time. It is also possible that only certain telephone numbers cannot be called.

While establishing a call, the message "No channel" may appear on FRITZ!Fon and one of the following error messages or another message regarding the telephone number is displayed on the "Overview" page or in the event log of the FRITZ!Box:

  • "[number] telephone numbers active, none of these registered"
  • "Registration of internet telephone number [number] failed. Reason for error: DNS error"
  • "Registration of internet telephone number [number] failed. Reason for error: Remote site not responding. Timeout."
  • "Registration of internet telephone number [number] failed. Remote site reports reason for error: [40x, 50x, 500, 503]"
  • "Internet telephony registration failed [number] Reason for error: [401, 402, 403]"
  • "Internet telephony with [Number] failed. Reason for error: [404, 405, 406, 407, 408, 50x]"
  • "Internet telephony with [number] via [registrar] failed. Reason for error: Not Acceptable Here (488)"
  • "Internet telephony with [number] via [registrar] failed. Reason for error: Timeout: The call was not accepted. [Message]"
  • "Internet (telephony) connection cleared."

Simply proceed as described below. After each measure, check whether the problem is solved.

Note:All instructions on configuration and settings given in this guide refer to the latest FRITZ!OS for the FRITZ!Box.

1 Entering your location information

  1. Click "Telephony" in the FRITZ!Box user interface.
  2. Click "Telephone Numbers" in the "Telephony" menu.
  3. Click on the "Line Settings" tab.
  4. Select your country from the drop-down list under "Location Information". If your country is not listed, select "Other country".
  5. For the "Country code", enter the leading zeros in the first field and the country code in the second field (for example, enter "00" and "49" for Germany, see fig.).
  6. For the "Area code", enter the leading zero in the first field and the area code in the second field (for example "0" and "30" for Berlin, see fig.).

    Fig.: Entering the country code and area code (e.g. for Germany and Berlin)

  7. Click "Apply" to save the settings and on the FRITZ!Box, confirm that the procedure may be executed, if you are asked to do so.

2 Restarting the FRITZ!Box

  1. Click "System" in the FRITZ!Box user interface.
  2. Click "Backup" in the "System" menu.
  3. Click on the "Restart" tab.
  4. Click the "Restart" button.

3 Deleting carrier prefixes (provider prefixes)

  1. Click "Telephony" in the FRITZ!Box user interface.
  2. Click "Call Handling" in the "Telephony" menu.
  3. Click on the "Provider Prefixes" ("Carrier Prefixes") tab.
  4. Delete all entries under "Global Provider Prefix" ("Global Carrier Prefix") and "Additional Provider Prefixes" ("Additional Carrier Prefixes").
  5. Click "Apply" to save the settings.

4 Disabling the landline settings

Since 2018, no new internet connections with landlines have been activated in Germany. New connections are always IP-based connections without splitters or NTs. In addition, almost all existing connections were converted to IP-based connections. Therefore, disable the landline in the FRITZ!Box to delete all settings that force calls to be made using landline connections if you no longer have a landline:

  1. Click "Telephony" in the FRITZ!Box user interface.
  2. Click "Telephone Numbers" in the "Telephony" menu.
  3. Click on the "Line Settings" tab.
  4. Disable the "Landline enabled" setting.
  5. Click "Apply" to save the settings.

5 Reconfiguring telephone numbers

  1. Click "Telephony" in the FRITZ!Box user interface.
  2. Click "Telephone Numbers" in the "Telephony" menu.
  3. Click the (Delete) button for the telephone number.
  4. Reconfigure the telephone number and select your internet telephony provider during setup.
  5. If you are unable to register the telephone number after setup, contact your provider to have them check your telephone number and login information.

6 The provider rejects the call attempt

This section only applies if the message "Internet telephony [...] failed. Reason for error: Not Acceptable Here (488)" is displayed under "System > Event Log" in the FRITZ!Box user interface when the error occurs. This message from your provider means that they do not make a requested function available for your line. This could be caused by the following reasons, for example:

  • The provider does not support the requested codec.
  • The provider does not support calls to the destination telephone number, for example calls to premium numbers.
  • The provider does not allow you to make more than one call at a time.

Therefore, a solution on the part of the FRITZ!Box is not possible.

7 Reconfiguring your telephone

  1. Click "Telephony" in the FRITZ!Box user interface.
  2. Click "Telephony Devices" in the "Telephony" menu.
  3. Delete the telephone that you cannot make calls with. To do so, click the corresponding (Delete) button.
  4. Use the wizard to reconfigure the telephone: To do so, click the "Configure New Device" button and follow the instructions.

8 Disabling HD telephony

  1. Click "Telephony" in the FRITZ!Box user interface.
  2. Click "Telephony Devices" in the "Telephony" menu.
  3. Click the (Edit) button for the respective telephone.
  4. Click on the "Telephony Device Features" tab.
  5. Click "Advanced Settings" to display all of the settings.
  6. Select the option "HD disabled" from the drop-down list in the section "HD Telephony".
  7. Click "Apply" to save the settings.

The FRITZ!Box is now fully configured for making calls over the internet. If you still have problems, your internet telephony provider may be experiencing technical difficulties.



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