ISDN telephone ISDN without function

Full of anticipation, I turned on my new phone after my Gigaset DX600 after years started to give up the ghost. But the anticipation was quickly marred. While following my Fritzbox worked fine, but the phone was just reacting to a MSN. Exclaimed one of outside another assigned to me to MSN, got the caller to hear the message: "The subscriber is currently unavailable"
For me it is one of the basic requirements that an ISDN phone can deal with multiple MSN.

Second drawback: the answering machine. Although you could record your own and save a text, only the caller always got to hear the phone in the existing pre-recorded announcement. Despite back and herprobieren the own announcement did not unlock.

And the PC software was faulty. They often showed in the display fields only a black screen, no text. The Synchro address from Outlook did not work either. I have saved since more than 400 contacts, choose but could only be good 20th

I consider myself as a little techie, who is looking forward to new things and like to try, but here worked nix. At least not at the time, I value.
So pack up everything and send back. Will probably now still be the Gigaset DX800.