Smart watch

I purchased two smart watches from groupon on the 21 /11/ 15. One of the watches were damaged. The smart watch did not have the buckle on it so it couldn't be worn. I called the call centre and they said they had no stock of the watch and I had to return both watches to get a full refund. why cant they give me a refund on the watch that is broken? if I buy 10 items from groupon and 1 item is defective do I have to return all 10 items? Groupon should review this policy. I will never buy from Groupon again.