Phone calls made easier with FRITZ!Box 6850: call directly via your SIM card's mobile telephone number

Making phone calls via the FRITZ!Box 6850 has always been straightforward: Simply obtain a phone number from an internet telephony provider, then enter this phone number as "Telephone Number" in the FRITZ!Box user interface, and you can make incoming and outgoing calls via this phone number with any phone connected to the FRITZ!Box. Sending faxes via an analog fax machine or the integrated fax function is then also possible.

With the new FRITZ!OS, calling is even easier, because it is now also possible to make calls directly via the mobile telephone number of the SIM card used in the FRITZ!Box 6850. You'll need a mobile phone plan that supports voice calls over a 4G LTE network (VoLTE).

How to set up mobile telephony in the FRITZ!Box 6850:

  • In a web browser, enter the address of your FRITZ!Box: "".
  • Once you've logged into the FRITZ!Box user interface, click "New Telephone Number" in the menu "Telephony / Telephone Numbers" and select "Mobile telephone number".
  • Now enter your mobile number (without the country code) in the corresponding field and click "Apply".

... and you're ready to start making calls.

Please note: If you use a multi-SIM card for the phone number on your smartphone in the FRITZ!Box 6850, your smartphone and your phone (registered on the FRITZ!Box) will ring at the same time. The phone that answers first receives the call. Outgoing calls can be made on both devices independently of each other in parallel.