Greyhound Bus complaint: Greyhound and its partner Bustang rejecting passengers with reserved tickets

On Jan 6th, our party of 6 with reservation 15974347 from Greyhound arrived at Frisco Transit Center 2h earlier awaiting for our bus to catch a flight at DIA. Our ticket is non-refundable however at the time of booking we were not aware it was partnered with Bustang. When Bustang bus CDT0713 arrived late, we were there first to drop our luggages, however the driver would not take Greyhound bookings but Bustang passengers and even cash passengers first. When it was our turn, we were told the bus was full and our party had to be split and only few of 6 was able to onboard. Another family of 4 was behind us was in the same boat. In order to catch our flight, the remaining party had to book another Bustang rider Pagasus and just to be told they were full and no available seating till close to our flight time. After wasting more time and money on Pagasus reservation in vain, we had to rush into Uber and cost us $170 to Denver Airport. There is a reason customers make advanced reservations so they can secure the ride, not to be standby and rejected when they have reserved tickets