One Travel Fare Difference After Qatar Airways Flight Cancellation

I booked return tickets with One Travel for three passengers from Vancouver (YVR) to Lahore (LHE) with Qatar Airways under booking number 93281329. The original trip was scheduled from March 6 to April 8, and I paid around 5,500 CAD in total. Due to the ongoing situation in the Middle East, the March 6 flight was cancelled. This cancellation was not caused by me in any way. After the cancellation, I was the one constantly calling One Travel and following up to find the earliest possible alternative, as it is very important for me to travel and see my mother. Eventually, they rebooked us for new dates, from March 23 to April 16. Now they are asking me to pay an additional 2,000–3,000 CAD as a fare difference, even though the change was triggered by the airline’s cancellation and not by any request from my side. I clearly explained to One Travel that this is not fair, because the cancellation and the delay in finding earlier options were not my fault. I also offered a compromise: if they cannot keep three passengers on the same flight, they could refund two tickets and rebook at least one passenger so that I can still travel to see my mother. Despite this, customer service told me they cannot waive the fare difference and kept pushing me toward a refund, which does not solve my situation, as the trip itself is extremely important for me. I request that One Travel arrange the March 23–April 16 itinerary (or the earliest possible alternative) without charging any additional fare difference, or reroute me appropriately at no extra cost. If they still cannot accommodate three passengers, I ask them to refund two tickets and at least rebook one passenger without any extra charge so that I can travel to see my mother. I expect One Travel to take responsibility for a situation that arose from a flight cancellation beyond my control and to provide a humane and fair solution instead of demanding a large additional payment.