Help with last order

I have an order with the number #2335888NA. Originally I was going to exchange only the bottom part of my set for another size but your team sent an email saying that no other sizes would be available by the time my package got back to your warehouse. So I went to your website and tried to generate a refund form for the whole item but that option is no longer available. Please help me. I would like to refund the whole MICA - BLUE BLOSS CHECK Crop Bikini Set.