Here's the pinout for the phone end:
http://pinouts.ru/CellularPhones-P-W/siemens_benq_pinout.shtml
Are you using these instructions for an RJ45 socket?
http://bobjohnson.nm.ru/inf/c55_jack.html
I suggest instead using this page, and an old AGP slot:
http://bobjohnson.nm.ru/inf/c55_cable.html
The reason is that the contacts inside the phone are raised, and the contact wires in the RJ45 socket are also raised, which makes it very difficult to keep them aligned when the plug is inserted. You may also have trouble finding a suitable socket. I have 32 network cards, and only 2 have the 2-piece socket needed.
The AGP slot (after being carefully cut) has grooves instead, like the original Siemens plug, and the AGP is long enough that you can try 3 or 4 times if you make mistakes. Of course, you need to find a bad motherboard with the AGP slot.
Unfortunately, the Google translator did not translate the text near the AGP connector (about half way down the page), so I do not know what the instructions say. However, I can see just from the picture that the old contact wires are pulled out, a piece of the slot is cut off leaving 12 contact positions, one side of that piece is cut off leaving an "L" shaped piece, then half of the remaining contact holder is trimmed away using a file, sandpaper, or a very thin hobby saw, and wires are pushed into the slots from behind. I made 2 AGP connectors, and they both fit my A56 perfectly.
