Air Canada Air Canada sell your ticket and keep you money Vancouver Nationwide

I bought tickets to Canada and a few days before the date of the return, I had an unexpected problem and could not use the back ticket. My wife had a seat next to mine, she would have enjoyed it if they have said that we were going to lose it. However we called the company and the clerk offered us a credit and said it would be valid for one year from THAT DAY (Nov,2015). Therefore, I did not checked in on that flight. If they were trustworthy and I was told that I was going to loose my money, I would have checked in and my wife would have traveled with the comfort of two seats that were paid by me. Now, I had to buy a ticket. I called on Air Canada, the clerk confirmed that I have a credit, took all my data, began to issue my ticket and at the end, he told me he was able to finish because my credit has expired. Why they said that I had until Nov/16 to use the credit? The company can not maintain the same information and plays with expectations of customers. I will never use Air Canada again and I recommend everybody the same!!