Sorry to hear your experience. A type change can be unfortunate, especially if there are fewer seats.

What mistake did the call centre make? Someone needed to be allocated seats in row 59, and I doubt they personally would know which seats have no windows. The same situation could occur with any airline.

Did you ask to pay for and exit row seat with more legroom, given you mention all 3 of you are tall?

That might be an idea for your return flight - I trust that goes well.