repeat modules purchased by accident

hello. first i realize i am unable to trade or gift modules but i thought i would at least ask the question. i have been a proud customer of dcs since 2011 when i purchased a10c. since that day i have had 11 more orders of various items (modules, terrains, and campaigns). somewhere along the way i managed to purchase repeats of a10c and combined arms. again i realize it was my fault and plan to take the nose-dive but wondered if i could return the repeats for refund or credit or coupon? thanks so much. and great game you have.