Can Baby Formula Be Returned To Any Store?

I bought some baby formula over the internet and I was wondering if I can take the formula back to any store that sells it?
I ordered Soy, but I wanted Dairy.
I know Whole Foods and Babies R Us carry Earth’s Best Organic formula.

How Long Can I Store Dry Baby Formula?

Im wondering how long I can store an opened can of dry formula. See, Im still mostly EBF my baby, I do have to give her formula rarely. I dont see a point to opening a WHOLE can (I have several unused/unopened cans) for 1-5 formula feedings a month. The can says it can be stored in a cool dry place open for one month. Is there any way to prolong storage (IE Freezing?) Thanks.