Incorrect information provided IN WRITING by an Airlink Reservations Support Agent NOT HONOURED by Airlink

Oh my word! 75% of the reviews are ONE star reviews! Well done, Airlink! Here's another one ...

I wanted to use a cancelled flight which I was told was valid until the 21st of April, to visit my mother on her birthday. This information was provided IN WRITING by an Airlink Reservations Support Agent. I had planned to use the flight on the weekend of the 20th of April. When I wanted to book a flight departing on the 19th of April, I was informed that the ticket was only valid until the 9th of April. Apparently the Airlink Reservations Support Agent had given me the incorrect information and I had planned the use of this ticket around this information. Ticket Wasted!

Whose fault is this? Surely, Airlink should honour the information that was provided IN WRITING by one of their staff members!? POOR CUSTOMER SERVICE, AIRLINK!!!