A Joke !!! Hum, noise, echo

I bought this phone because of the many good reviews. Unfortunately, this was a mistake now as it turns out.
The phone I operate on a Fritz! Box 7330, which is connected to a normal telecom analog connection (no IP connection).

Now, when you make a call, you can hear in the Fritz! Fon a hum is heard during a call echoes, yes, and even a noise. From Fritz although there is a support article that describes this / these problem (s) and for demonstrating solutions. Unfortunately, none of these has brought an improvement described instructions. (Uploading the latest firmware on the Fritz! Fon and FRITZ! Box, disconnecting all connected devices [USB HDD, Ethernet] etc.)
The hum even hear the person on the other end of the line.

Such a bad quality I had a producer as AVM not have believed that I had been really only good experiences with the products for this manufacturer.

Previously I had a simple Gigaset own DECT base station on the Fritz! Box on the analog port. The Gigaset there were no problems. Call quality was absolutely flawless !.

I will return the phone to Amazon and look around for another possibly Gigaset.