Hi Experts,
I need help on how to pursue my case.

I had a 7 day reservation with alamo at SFO airport. When I landed at airport to pick up the car, they said my coupon has expired ($50 off on weekly rental). and I have to pay $65 more to get the car. That time I denied the car and taken from national (Hopefully i had another booking)

Later I have written couple of emails to them and called customer service. Every just say "your coupon was expired". And I ask "how will i know if your website does not know"

I want to pursue it further and get some compensation for the incovieance.

What is the best way to pursue it further?