If you bought the headbands via three individual purchases, as your post appears to suggest given that you said that the seller supplied three separate returns labels, then you should have used all three returns labels and sent the headbands back to the seller individually, one in each package. The reason for this is because each headband would have had an associated returns label with its own tracking number assigned to it, and if the tracking recorded against each returns label proved attempted or successful delivery to the seller and you had not been refunded then eBay would have forced the refund for each headband that you had not received a refund for.
In light of the fact that you only used one postage label and sent all three headbands back in the same package you've effectively put yourself at a disadvantage, as the seller could quite easily tell eBay "I never received all three back again - the buyer returned two headbands in one package, so I refunded the buyer for what I got back." With no way of being able to disprove an allegation of this nature you're going to find it far more difficult to get your money back for all three headbands.
Going forwards, if you wish to purchase more than one of the same type of item from a seller then if he/she doesn't have the option on the listing to select the quantity that you want to buy then when you select the first one add it to your basket to start with rather than paying for it straightaway. (It's best to ensure that your basket is empty before you start so that you don't end up paying for items from different sellers in one go when you go to Checkout, as you don't want to make things more complicated than they need to be.) Repeat the process as many times as necessary until you've got as much as you want to buy from that seller, then pay for all of the items in one go at Checkout.
If you use the option explained in the previous paragraph then if you subsequently wish to return the items you will only need one returns label. If, however, you want to keep some and return others you can still use one returns label only, as the seller would only need to issue a partial refund in that instance relating to the value of the returned items, as opposed to a total refund.
