I have several different handset types on my PBX extensions and most had the USA ring & ringback tones instead of the Australian (AU) tones I wanted. I found I had to change the settings on the actual phone handsets rather than the PBX.
I had to do this change on a Cisco SPA303 and a Grandstream GXP1610 to make them sound correct.
Some phone (eg Yealink T23G) have a dropdown list of countries to set the tones for you, which makes it easy.
Others, like my SPA303, require you to type in a complicated series of codes. If you are in that situation, you might have to search the web to find the correct sequence of codes for German ring tone.
.
