provided by Star2Billing S.L.

callback was working, but after i type reload in asterisk cli, every time i try call back, it shows
== Auto fallthrough, channel 'SIP/philipow-08c8b868' status is 'UNKNOWN'
any idea at all?

That sounds like your Asterisk dialplan may have changed. There should be a message on the line above mentioning that it could find the extension/priority/context that the call was delivered to.

-- Executing [philipow@from-pstn:1] Set("SIP/philipow-08c8b868", "__FROM_DID=philipow") in new stack
-- Executing [philipow@from-pstn:2] GotoIf("SIP/philipow-08c8b868", "0 ?cidok") in new stack
-- Executing [philipow@from-pstn:3] Set("SIP/philipow-08c8b868", "CALLERID(name)=16473678909") in new stack
-- Executing [philipow@from-pstn:4] NoOp("SIP/philipow-08c8b868", "CallerID is "16473678909" <16473678909>") in new stack
-- Executing [philipow@from-pstn:5] Goto("SIP/philipow-08c8b868", "a2billing-cid-callback|16473678909|1") in new stack
-- Goto (a2billing-cid-callback,16473678909,1)
-- Executing [16473678909@a2billing-cid-callback:1] Ringing("SIP/philipow-08c8b868", "") in new stack
-- Executing [16473678909@a2billing-cid-callback:2] Set("SIP/philipow-08c8b868", "CALLERID(num)=") in new stack
== Auto fallthrough, channel 'SIP/philipow-08c8b868' status is 'UNKNOWN'

that is all the msgs i got

You may need a hangup after calling cid-callback.. otherwise the channel doesn't know the status of the channel.