Am I obliged to give a refund if the person changed their mind about product?

[Soria61]

I sold a concert ticket to someone through goods and services with an invoice yesterday I also didn’t include no refunds in the invoice. The concert is tomorrow and the buyer just now told me that they’d like to return the ticket as they have changed their mind about attending. Am I obliged to refund them especially since it’s so close to the concert date?

[1Moparlover]

Hi...I just had a similar issue.  A guy from Mexico says someone else used his account to buy something.  Wants a refund months after the sale?  How did your transaction turn out?  Did you have to issue a refund?  Thanks.