Poor comfort with good quality telephony

Unfortunately, the device can not the basic telephony features:
a. No number display to the answering machine
b. very complicated query the ABs over several keys
c. very cumbersome call from phonebook (duplicate keys necessary as with many Siemens / Telekom devices
d. no number transfer from the redial in the phonebook possible
etc.
Summary: Too bad I do not even know Tiptel
How do I choose the device as one of the few ISDN devices without radio, but the functions are simply inadequate.