before installation:

[root@emami freeswitch]# pwd
/usr/local/src/freeswitch
[root@emami freeswitch]# vim modules.conf

#applications/mod_blacklist
applications/mod_callcenter
#applications/mod_cidlookup
applications/mod_cluechoo
applications/mod_commands


after installation:
freeswitch@internal> status
UP 0 years, 0 days, 0 hours, 10 minutes, 25 seconds, 715 milliseconds, 274 microseconds
FreeSWITCH (Version 1.5.3b git 9ed53db 2013-07-06 00:50:57Z) is ready
0 session(s) since startup
0 session(s) - 0 out of max 30 per sec
1000 session(s) max
min idle cpu 0.00/94.00
Current Stack Size/Max 240K/8192K

freeswitch@internal> module_exists mod_callcenter
false

freeswitch@internal> mod_callcenter reload
-ERR mod_callcenter reload Command not found!