Theft of money

My wife and I prebooked and paid for seats form Schiphol to Cape Town to ensure we were sat together. The seats were confirmed at on line check in and via email. Upon arrived at check in at the airport the seats were changed and were were sat well apart. I am recovering from cancer and it was important to be sat together. When enquiring about a refund for over £110. We were told they do not refund seat bookings. This is ********* theft of money from a customer and the breaking of a contract. Beware of booking for seats and other on boards extras. KLM can simply change the terms and conditions