Just in case you're not aware of this, most Siemens phones that
support "AT" commands over a serial connection (cable, IrDA, or
Bluetooth) implement a Siemens-specific command, "AT^SSTK",
which lets you run STK (SIM Toolkit) TLV (Tag, Length, Value)
commands over the serial connection.  This might be a useful
introduction for you.  Personally, this has been my only
programming exposure to STK, and I use it to gather
netmonitoring information.

I take it you've got a copy of GSM 11.14 (STK specification).
You can read a Siemens phone's STK Profile with "AT^SSTK=?",
getting a response like "^SSTK:
7FFFFFFF7F0F00DF7F00001F2300000003".  From there, it's a matter
of constructing GSM 11.14 TLV commands conforming to this
profile, and interpreting the results.

The Siemens documentation mentions the "AT^SSTK" command without
really telling you how to use it.  Basically, you enter a
command like

       AT^SSTK=99

where "99" is the length (or a larger number) of the TLV command
you're running.  Then you wait for the ">" prompt, and enter
the TLV command itself terminated with <ctrl-Z>, eg

       D009810301260082028381

You'll receive a response like:

       ^SSTK: 810301260082028281830100930705F51010301401

If nothing else, the above examples might serve as an
introduction to TLV syntax.  I can work through them with you
if you need to do that.

John

Sim Toolkit development has definitelty become easy now after SIM card
vendors have agreed on having an Interoperable STK. So, there are
Interoperable guidelines also do develop STKs. Its no longer
proprietary.

The best approach is to download 11.14 and GSM 03.19 Technical
Specifications from etsi.org and then try it on your own.

Hope this helps!
Cheers