For me, the only thing that really seemed to get them going was when I threatened to contact the customer... I ended up having to contact the customer to let them know I had not yet been paid, and I believe they put pressure on MS Transportation to make things right...
We have been trying to collect on an invoice from MS Transportation from Apr 2016, with many empty promises and no payment. They are now on our do not use list.
BE ALERT, just tried to call MS Transportation, there is something weird with their phone systems, as well as, no ability to leave a voice message due to being full.