Not mature! Bad buy!

8 months now I use the AVM FRITZ! Fon, first in connection with a Fritz! Box 7270 and now currently working on a FRITZ! Box 7390th
So super pleased I am with the boxes of AVM, so I am dissatisfied with the phone. The voice quality for me is absolutely inadequate, despite good signal quality (distance from the box about 5 feet!) And the ability to adjust the timbre individually by an equalizer, the problem is the one that disconnects sporadic. Well, there are indeed offered in some intervals firmware updates, I thereby hoped for improvement. This remained the case with the now current firmware FRITZ OS 05.58-26237 BETA and the FRITZ! Fon MT-F version:! 1:03:01 of sadly. Add to this that I have to start by sporadic calls the new machine, in which I remove the battery, as the device freezes as soon as the connection has been terminated. Of course I have repeatedly written to the support of AVM, Unfortunately the solutions offered by the friendly staff bring a satisfactory solution. Basically, the possibilities offered by the phone are quite interesting and would absolutely delight me. But what should I do with the possibility of retrieval of media content and playback on the phone (AVMFritz! Media Server) or the display of newly received emails / RSS news or podcasts when I have serious problems with the phone (!)?
Once a telephone from AVM? No. Therefore, 1 star, because practicality looks different.