Brussels Airlines Changed My Paid Seat Twice and Ignored My Refund

I booked my flights with Brussels Airlines and paid extra to get a specific seat. However, they changed it twice, once on the way out and once on the way back. It bothered me even more that I had picked and paid for that seat because it was important to me, but my choice was ignored. I called customer service, but they kept passing me from one agent to another without giving me a real answer or taking responsibility. It doesn't help that getting a refund for the seat is not easy. The only thing I can do is go through their complicated complaint process, where they want me to pay €55 just to get back the €30 I already spent. It seems unfair and makes me wonder how much Brussels Airlines cares about its customers.