Your Vendor may block you becaus of G711 or any other codec calls. So Check how to send G729 Only to vendor end. Go to routing gw > additional settings >> edit >> codec >> sip … double click the codecs g729, g729D, g729E these three (select, right click and add) and also check mark ‘Softswtich Specified’ must. You can do the same for client mapping gw too.
