Calls disconnecting

I have the users complaining that their telephone calls keep disconnecting in the middle of a call frequently. When I check the logs, I find these lines. How can I solve this issue?
This is after I gave the command tail /var/log/asterisk/full.
May 13 18:38:59 NOTICE[32187] cdr.c: CDR on channel ‘SIP/200-b7507ec8’ not posted
May 13 18:38:59 NOTICE[32187] cdr.c: CDR on channel ‘SIP/200-b7507ec8’ lacks end
May 13 18:40:15 NOTICE[32215] cdr.c: CDR on channel ‘Zap/3-1’ not posted
May 13 18:40:15 NOTICE[32215] cdr.c: CDR on channel ‘Zap/3-1’ lacks end
May 13 18:41:40 NOTICE[32222] cdr.c: CDR on channel ‘SIP/200-b7507ec8’ not posted
May 13 18:41:40 NOTICE[32222] cdr.c: CDR on channel ‘SIP/200-b7507ec8’ lacks end
May 13 18:58:29 NOTICE[32362] cdr.c: CDR on channel ‘IAX2/111-4’ not posted
May 13 18:58:29 NOTICE[32362] cdr.c: CDR on channel ‘IAX2/111-4’ lacks end
May 13 19:03:33 NOTICE[32440] cdr.c: CDR on channel ‘SIP/301-b7507ec8’ not posted
May 13 19:03:33 NOTICE[32440] cdr.c: CDR on channel ‘SIP/301-b7507ec8’ lacks end

Please don’t post multiple times a hour or so apart. This is community based support and when somebody has time to answer they do. But finding multiple postings will not get you a answer any faster and just generate a ton of noise that people will get upset about.

I’ve responded at http://www.freepbx.org/forum/freepbx/users/telephone-calls-disconnecting-issue