Same line on a similar Span always busy

Hi

Below are some logs, can any one put some light on what is happening here, what i am trying to highlight is that everytime a call is hitting 0/22 on Span 2 it is going on 0/28 of Span 2 and the getting Hung up with cause 31, also you can see that there are more then one call coming on the same channel 0/22 at the same time

[Jul 8 21:31:03] DEBUG[12290] chan_dahdi.c: Ring requested on channel 0/22 already in use or previously requested on span 2. Attempting to renegotiate channel.
[Jul 8 21:31:03] DEBUG[12290] chan_dahdi.c: Found empty available channel 0/28
[Jul 8 21:31:03] VERBOSE[12290] chan_dahdi.c: – Accepting call from ‘9954225006’ to ‘588321224027’ on channel 0/28, span 2
[Jul 8 21:31:03] VERBOSE[12290] chan_dahdi.c: – Channel 0/28, span 2 got hangup, cause 31
[Jul 8 21:31:06] DEBUG[12290] chan_dahdi.c: Ring requested on channel 0/22 already in use or previously requested on span 2. Attempting to renegotiate channel.
[Jul 8 21:31:06] DEBUG[12290] chan_dahdi.c: Found empty available channel 0/28
[Jul 8 21:31:06] VERBOSE[12290] chan_dahdi.c: – Accepting call from ‘9678691089’ to ‘588321224030’ on channel 0/28, span 2
[Jul 8 21:31:06] VERBOSE[12290] chan_dahdi.c: – Channel 0/28, span 2 got hangup, cause 31

[Jul 8 21:31:17] DEBUG[12290] chan_dahdi.c: Ring requested on channel 0/22 already in use or previously requested on span 2. Attempting to renegotiate channel.
[Jul 8 21:31:17] DEBUG[12290] chan_dahdi.c: Found empty available channel 0/28
[Jul 8 21:31:17] VERBOSE[12290] chan_dahdi.c: – Accepting call from ‘9957988816’ to ‘588321224030’ on channel 0/28, span 2
[Jul 8 21:31:17] VERBOSE[12290] chan_dahdi.c: – Channel 0/28, span 2 got hangup, cause 31

[Jul 8 21:31:18] DEBUG[12290] chan_dahdi.c: Ring requested on channel 0/22 already in use or previously requested on span 2. Attempting to renegotiate channel.
[Jul 8 21:31:18] DEBUG[12290] chan_dahdi.c: Found empty available channel 0/28
[Jul 8 21:31:18] VERBOSE[12290] chan_dahdi.c: – Accepting call from ‘8011569822’ to ‘588321224030’ on channel 0/28, span 2
[Jul 8 21:31:18] VERBOSE[12290] chan_dahdi.c: – Channel 0/28, span 2 got hangup, cause 31
[Jul 8 21:31:18] VERBOSE

Any help would be appriciated

Thanks
Abhi