Too many RINGS without answer from SIP remote extensions

Dear friends,

We have configured 5 remote extensions via SIP protocol. Addtionally we have defined trunks to our VOIP service provider.

When we call from some remote extension to a local Mobile phone, the ring start for the caller for almost 12 or 15 RINGs before hearing on the called size. Sometimes the timeout expire and cannot make the call.

BUT, for other local Mobile phones there is absolute no problem.

We have take debugs for the two phones and found that:

The telephone THAT DO NOT WORK have :
“SIP/2.0 183 Session Progress” instead of the message of
"SIP/2.0 200 OK", at the same step secuence of the call that work.

Looking in the forums we find this link:

that mention a problem with the parameter progressinband of the default SIP.CONF, so we change it into progressinband=no. (related the early media capability that some telephony operators use)

In another forum we find that we should remove the “r” of the extensions_additional.conf file, parameters : DIAL_OPTIONS and TRUNK_OPTIONS

But we continue with the problem. Any suggestions?

Thanks and Regards