Hello, i am a voip Engineer with more than 7 years of expertise in the field, i got very good knowledge working with voip systems like kamailio, freeswitch, asterisk and opensips, your options here are to use kamailio, opensips or freeswitch to make the custom headers to send it to your trunks, i can help you to deploy one of the mentioned systems and seek for the correct setup to make it work with your needs. if you are interested to talk regarding this, hit me on chat or add me over skype: montana3601