In January, my wife and I booked through our local travel agent. We were planning our trip to Europe in September, and because I am disabled, decided to book well in advance to secure comfortable seats, on which we paid an upgrade fee, and thereby ensure are seats would be secured and guaranteed (so we thought). KLM had the best routing and the least number of stops. We confirmed and paid for our flights in January, 2017, seven months in advance of travel. Prior to departure we checked with our travel agent that the flights were all in order. The day of our flight, we arrived at the check in counter and we were told we were not on the flight. After an hour of talking to airline agents and contacting our travel agent, we were told that KLM had change our flight arrangements last night and we were now flying Air Canada via Toronto to Europe. We ended up flying "Charter Class" to Toronto with Air Canada in seats that were uncomfortable, little leg room, and my wife and I were not able to sit together! When we asked for a change to seats together we were advised the plane was full. We were forced to fly 4 hours to Toronto in cramped conditions sitting apart. On the next leg of our trip, Toronto to Amsterdam, we were not given upgraded seating as we had paid for on KLM; upon enquiring we were advised only one upgrade seat was available on the Air Canada flight. Further, our travel documents did not provide for any advisement for disability transfer assistance and we had to make our own way. Despite our disappointment with KLM for this shabby rescheduling on their part, presumably do to with over selling their flights, we were again disappointed when we complained about our treatment when we got home. KLM claimed the rescheduling was not their responsibility. Our frustration grew when our travel agent confirmed KLM were in fact the culprit. Again this was pointed out to KLM and their lame response was a "boiler plate" apology together with a $100 voucher for a flight on their airline within the next six month. This is worthless to us as we shall NEVER fly KLM again.