eBay

Hello,A buyer asked for a replacement. i know that in the returns there have to be an option for replacement or exchange ", but there is not! see in the attachment. what can i do? thanks for any help!

i sold an item , that i had 1 piece of it in stock. later i seen that another piece was sold.the listing is "good till cancelied" , the " use the out-of-stock option is marked.what am i doing wrong? and now what shall i tell the second buyer? how can...