Online travel ticket a scam?

I booked online and paid 28 Sept 2017 for PE to London return ticket R8904.84 Everything was confirmed, my e-ticket emailed to me. Happy days. I get to the airport on 17 Oct 2017 for BA staff to inform me that Tripsta booked me, and then cancelled me off passenger list! I was forced to buy a single from PE to Jburg for R2271.69... rip-off, but what else can I do, I had to be in the UK for work. When I get to Jburg, the chaos ensues. I spend 16 mins on a customer services call to Tripsta, for Allen to confirm all is in order. NOT. Qatar cannot check me in. My ticket is now reading ''out of sequence''. The manager instructs me back to BA, and for them to change status on original ticket, with printouts before and after, to show Tripsta that they are in fact at fault! Now they still won't refund me for the second ticket I had to buy. What an absolute useless company. Qatar says many dodgy scamming agents online...