Have you configured a codec class with codeg g729 under voice register pool ?

yes I do.

voice class codec 1

codec preference 1 g729r8

codec preference 2 g711alaw

codec preference 3 g711ulaw

voice register pool 2

id mac 0000.0000.0000

number 1 dn 2

username XXX password XXX

!

voice register pool 4

id mac 001A.2FA6.F21E

number 1 dn 4

dtmf-relay sip-notify

voice-class codec 1

username XXX password XXX

pool 2 is initiator of connection I've removed voice-call codec to force use only g729

You need the voice-class on both. You cannot force use of a codec.

This doesn't matter it just select g711u always.

In the phones, select g729.

This doesn't work either. I even change one phone to cisco7940.

On the trace you sent, cause code 65 is bearer capability not implemented, meaning codec mismatch.

Take a trace again with the proper voice-class set on both voice register pool, and send it here with the configuration.

Same reason cause=65, its running on: c2800nm-advipservicesk9-mz.124-15.T3.bin

Currently I have some problems with testing because NAT incorrectly translate sip headers(IOS bug), when have two outside interfaces.

I will continue testing on site tomorrow Monday.

I choice g729r8 codec alone on voice register pool. And its clear cisco don't like some settings of g729 from my third party phone.

voice register pool for called has g729 also ?

exactly same.

Are both phones registered ok with CME ?

yes both phones registered fine, I see no problem in registration when check logs. Tomorrow we will receive bunch of 7911 phones, hope this help isolate problem.