From software 2.33 it is possible to upgrade an N670 Single cell to an N670 multi cell.
For this you need to add a license. In the N670 web-interface go to: System - Licensing
Before the license upgrade
An N670 can not be used as DECT base only. If you want to create an multi cell system, you need to add N870 DECT bases.
In case you need to remove this license you have to do it via the cli interface with "sudo reset2factory hard".
When connecting an N670 behind an Virtual Integrator or N870 in the role Integrator only then.