Finally, I think I’ve found the problem:
I programmed the four channels of one of my clients who has a NEC PBX with us and… surprise! his trunks work fine but the two mine doesn’t work although they appears as “register OK” at the sip show peers.
I thinks my trixbox is not working well, if you configure the lines with freepbx and you have this three configurations of same provider the systems seems to be crazy, very slow registering, the phones appear unrechable on “sip show peers” and if I delete my two trunks and let the last one all comes to be perfect.
May be Asterisk or trixbox is not prepared to wor with more than one trunk of the same provider?
I want to give thanks to all people who helped me with this issue, specially to David55.