Caller ID name is 'unknown' number is 'unknown'

New installation. I keep getting Unknown caller id every 20 to 30 minutes. We are connected to 5 analogs PSTN using digium TDM8000 cards. As soon as it is answered it hangs up. What could be causing this? Would phone company be sending signals?
Thanks

From my log file. The message is at the very end.

[Nov 13 10:32:48] VERBOSE[7082] logger.c: – Executing [350@ext-group:10] Set(“Zap/1-1”, “RecordMethod=Group”) in new stack
[Nov 13 10:32:48] VERBOSE[7082] logger.c: – Executing [350@ext-group:11] Macro(“Zap/1-1”, “record-enable|309-306-312|Group”) in new stack
[Nov 13 10:32:48] VERBOSE[7082] logger.c: – Executing [s@macro-record-enable:1] GotoIf(“Zap/1-1”, “0?2:4”) in new stack
[Nov 13 10:32:48] VERBOSE[7082] logger.c: – Goto (macro-record-enable,s,4)
[Nov 13 10:32:48] DEBUG[7082] app_macro.c: Executed application: GotoIf
[Nov 13 10:32:48] VERBOSE[7082] logger.c: – Executing [s@macro-record-enable:4] AGI(“Zap/1-1”, “recordingcheck|20081113-103248|1226590360.486”) in new stack
[Nov 13 10:32:48] VERBOSE[7082] logger.c: – Launched AGI Script /var/lib/asterisk/agi-bin/recordingcheck
[Nov 13 10:32:48] VERBOSE[7082] logger.c: – AGI Script recordingcheck completed, returning 0
[Nov 13 10:32:48] DEBUG[7082] app_macro.c: Executed application: AGI
[Nov 13 10:32:48] VERBOSE[7082] logger.c: – Executing [s@macro-record-enable:5] NoOp(“Zap/1-1”, “No recording needed”) in new stack
[Nov 13 10:32:48] DEBUG[7082] app_macro.c: Executed application: Noop
[Nov 13 10:32:48] VERBOSE[7082] logger.c: – Executing [350@ext-group:12] Set(“Zap/1-1”, “RingGroupMethod=ringall”) in new stack
[Nov 13 10:32:48] VERBOSE[7082] logger.c: – Executing [350@ext-group:13] Macro(“Zap/1-1”, “dial|12|tr|309-306-312”) in new stack
[Nov 13 10:32:48] VERBOSE[7082] logger.c: – Executing [s@macro-dial:1] GotoIf(“Zap/1-1”, “1?dial”) in new stack
[Nov 13 10:32:48] VERBOSE[7082] logger.c: – Goto (macro-dial,s,3)
[Nov 13 10:32:48] DEBUG[7082] app_macro.c: Executed application: GotoIf
[Nov 13 10:32:48] VERBOSE[7082] logger.c: – Executing [s@macro-dial:3] AGI(“Zap/1-1”, “dialparties.agi”) in new stack
[Nov 13 10:32:48] VERBOSE[7082] logger.c: – Launched AGI Script /var/lib/asterisk/agi-bin/dialparties.agi
[Nov 13 10:32:48] VERBOSE[7082] logger.c: dialparties.agi: Starting New Dialparties.agi
[Nov 13 10:32:48] VERBOSE[7085] logger.c: == Parsing ‘/etc/asterisk/manager.conf’: [Nov 13 10:32:48] VERBOSE[7085] logger.c: Found
[Nov 13 10:32:48] VERBOSE[7085] logger.c: == Parsing ‘/etc/asterisk/manager_additional.conf’: [Nov 13 10:32:48] VERBOSE[7085] logger.c: Found
[Nov 13 10:32:48] VERBOSE[7085] logger.c: == Parsing ‘/etc/asterisk/manager_custom.conf’: [Nov 13 10:32:48] VERBOSE[7085] logger.c: Found
[Nov 13 10:32:48] VERBOSE[7085] logger.c: == Manager ‘admin’ logged on from 127.0.0.1
[Nov 13 10:32:48] VERBOSE[7082] logger.c: dialparties.agi: Caller ID name is ‘unknown’ number is ‘unknown’