Asterisk after version 11 question about TXCNT cmd

I used asterisk-11.16.0 iax2, at this version, asterisk will release channel after caller and callee transfer, the transfer setup action start by asterisk’s TXREQ, and caller and callee’s TXCNT/TXREL… cmd.
My question is when I use newer version after 12, it seems that no iax2 native brange for TX* cmd, on newer version how to use TX* cmd, it seems that the TX* cmd started by asterisk server.