Too small

I got a pair of sandals delivered today from an online store I tried for the first time. I thought for sure I am 6 ½ on flat sandals so I got that size only to find out today it's a little small. I can't believe I have to settle for a 7 from now on. Well, it actually depends on the brand just like on clothes. They all differ on sizing. Anyway, I have to return them tomorrow and perhaps get a different style if not just get a refund. I have to think about whether I really like the style or not. They really look great and feels comfortable. It's just that my left foot feels too snug compared to the right one which is just fine. I can live with half a size bigger so I might exchange them for a 7. Now, off I should to printing the free pre-paid return label! Ciao!