[ahgh1999]

I need to know how to claim British Airways and make a complaint regarding BA’s conduct and customer support as I was denied boarding my booked connecting flight by British Airways.
My mom and I had round-trip flight from Shiraz to Calgary through the connections Istanbul TK 885, London BA 675 and AC 851 Calgary all dated March 06, 2018.
My mom and I were checked in Shiraz airport on March 06, 2018 and received our boarding passes for all roots by Turkish airline. However, British Airways staffs had denied us to get on board the flight BA 675(Istanbul–London) in Istanbul with no reason and clarification just because we are Iranian passport holders. We were quite legal passengers to Canada with the valid passport; visa and all boarding pass in hand. British Airways staffs impolitely and aggressively refused us get onboarding. Additionally, British Airways not accommodating us for reaching any replaced flight for our next connecting flight London to Calgary AC 851 and we missed our flights, correspondingly. I never expect it was the way that a large company like British Airways or Star Alliance Member Airlines would conduct business like that with us.
British Airways left us alone with zero assistance and customer service in Istanbul and it made us 8 hours confusion, worse fear and anxiety actually how to manage this awful condition. I inevitably decided to pay CAD2723 (by myself) to take the flight to Calgary through Toronto.
As I and my Mom had borne stressful condition, losing our time and money, I have a strong objection and complaint regarding the unprofessional and impolite British Airways conduct. Now, who can I please direct to claim British Airways in the right way due to making a stressful condition, losing our time and costing us additional CAD2723?