This looks perfectly normal (at least from asterisk's point of view). Here is a call being answered and clearing down on one of our test servers...(it looks just the same as yours except we cleared down normally from the sending phone.
-- AGI Script selintra completed, returning 0
-- Executing [4008@internal:1] AGI("Zap/1-1", "selintra|InCall|") in new stack
-- Launched AGI Script /var/lib/asterisk/agi-bin/selintra
-- AGI Script Executing Application: (Dial) Options: (SIP/4008|10|t)
-- Called 4008
-- SIP/4008-08a5e940 is ringing
-- SIP/4008-08a5e940 answered Zap/1-1
-- AGI Script selintra completed, returning -1
== Auto fallthrough, channel 'Zap/1-1' status is 'ANSWER'
-- Executing [h@internal:1] Hangup("Zap/1-1", "") in new stack
== Spawn extension (internal, h, 1) exited non-zero on 'Zap/1-1'
-- Hungup 'Zap/1-1'
Something is driving a hangup event into asterisk. Run a SIP trace to verify this...
install ethereal if you don't already have it
yum install wireshark
Then run
tethereal -R sip -f "host the-budgettone-url"
Now make your inound call and look for the hangup (BYE) request being sent.
If it is the carrier then you'll need to speak with them.