show codec shows the codecs that FreeSWITCH can handle, but it does *not* show specific codecs your SIP profile is using. Look in your SIP profile (internal.xml or external.xml or whatever) and check out the codec_prefs.
The reason Anthony knew you only had GSM is because of the "audio codec compare" lines in the log:
> 2012-02-15 11:34:52.894480 [DEBUG] sofia_glue.c:4801 Audio Codec Compare [PCMA:8:8000:20:64000]/[GSM:3:
8000:20:13200]
> 2012-02-15 11:34:52.894480 [DEBUG] sofia_glue.c:4801 Audio Codec Compare [PCMU:0:8000:20:64000]/[GSM:3:8000:20:13200]
> 2012-02-15 11:34:52.894480 [DEBUG] sofia_glue.c:4801 Audio Codec Compare [telephone-event:101:8000:20:0]/[GSM:3:8000:20:13200]
Note that the only codec that FS tries to match against is GSM. If other codecs were set in your inbound codec prefs then you'd see those being listed in "Audio Codec Compare" as well.
-MC