SAS did not save my reserved seats any suggestions?
 

I need help. I completed my reservation by phone in order to secure window seats due to health condition. I was given reserved window seats. Upon 3 days prior to my flight, I was told when I called back that I had no reserved seats! It is an 8 hour long international fligt. I was told that there are no more window seats for my outgoing flight. How can I get them to upgrade my seat to a window due to their error? Any suggestions? Leaving July 14th. Thanks