This is for customer using Asterisk flavored PBX. icesupport is enabled by default that causes the call to hangup right after 200 OK. As of writing of this document, DIDForSale registered sip trunk with asterisk does not support icesupport.

Ice support can be disabled in /etc/sip.conf.

ssh login in asterisk.

Some pbx might have this setting in sip_customer_general.conf file