Booking with Travelstart

I am writing this review after a completely unacceptable experience with a flight booked through Travelstart. I booked my ticket 2 months in advance for a flight on [Insert Date of Flight Here] with booking reference [Insert Travelstart Booking Reference Here]. Upon arrival at the check-in counter, I was informed by the airline staff that there was no confirmed seat for my booking because it was a "very 3rd party booking through Travelstart." I was then forced to wait at the counter until all other passengers had checked in, creating an extremely stressful and embarrassing situation. My seat was only secured at the last minute because another passenger's booking was cancelled. As this was a trip for a very few days of holiday, this stress and wasted time severely ruined the start of my break. I demand an immediate explanation from Travelstart as to why a booking made two months in advance was not properly secured with a confirmed seat, and I expect fair compensation for the severe inconvenience, distress, and near-denial of boarding I experienced.