Please go to your customer portal and there to "Phone settings" → "Manage numbers". You will see an overview of your phone numbers and next to it the mode of the phone number in a blue field.
In our example screenshot, you can see that one of the phone numbers has already been transferred to the Cloud Telefonanlage ("PBX" in the blue button). The second number shown is not yet available in the Cloud Telefonanlage ("Trunk" in the blue button).
Click on it to adjust the mode.
A selection screen opens with modes that are available for the respective call number type. Call number blocks, for example, have fewer options.
Now please select the PBX mode "Cloud Telefonanlage (hosted PBX)" and then click on "Apply".
Attention. Virtual DDIs and settings of the trunk are deleted by this!
In the overview you can now see that the selected phone number is also in PBX mode.
You can now assign it to extensions in your Cloud Telefonanlage.