Incorrect info provided

I booked and paid for return tickets for 2 to Amsterdam as per the process when applying for the Schengen Visa and the agent advised if the Visa is denied I will get a full refund, the visa was denied and i did not receieve a full refund, only to query it and then find out that The tickets i purchased were non refundable tickets hence only the portion of the airport taxes was refunded. How unprofessional is this? Yet i called the contact centre on numerous times and was always given the same info, i wouldn't recommend KLM Dutch airlines to any family or friends.