Based on the error message, it seems that you attempted to remove the phone line from a device which has not been assigned to any extension. Please check if it is the case.

The API is for unassigning a device which was assigned to an extension.

Yes this was problem.

Thank you

But now I have another issue.I want to assign this phone number to an other extension with:
Phone Numbers - Assign Phone Number

But with this request

curl --request PATCH

--url 'https://platform.devtest.ringcentral.com/restapi/v2/accounts/~/phone-numbers/400408004'

--data '{"usageType":"PhoneLine","extension":{"id":"896916005"},"type":"VoiceFax"}'

I got the follwing error:

{

"errors": [

{

"errorCode": "CMN-101",

"message": "Parameter [type] value is invalid",

"parameterName": "type"

}

]

}

I tried also other types but every time the same error

{ "errors": [ { "errorCode": "CMN-101", "message": "Parameter [type] Wert ist ungültig.", "parameterName": "type" } ] }

Don't set the type parameter. OR if you set it, it must be the same as the type of that number. You can read the number info using this API.

Note: This does not support PhoneLine (Digital Line). Only CompanyNumber and DirectNumber