as you know- i am not 100% in love with how my new chanel sunnies feel, but i put my 150 gift card toward them. They were 350 after tax. What happens to my gift card if I return them? They are on my SAKS credit card along with my GST- would I lose it or would it even be possible to lower my bill by the total amount of the shades? (that would be great!-like 150 off the purse)