Hi Macsu,
As pointed out by @ryanwanner, you can add a "No Refund" policy to both your receipts and checkout screens however, there's no guarantee doing so is protection for you, but still this is a "good business practice". Just be clear with your policy as to why you have a "No Refunds". Square does have info concerning Chargebacks - see this info.
The downside is - it's up to the customer's credit card issuer and/or bank to make the final decision and sadly in many scenarios, the decision favors the customer and/or buyer. A customer or buyer can report an unauthorized purchase, a defective product or item or failure to provide advertised services. Note, you do or should have the opportunity to file a counter explanation on your behalf with credit card issuer and/or bank.
Something to consider. Having a flexible refund policy in place allows you to negotiate with the customer and/or buyer by offering other solutions, i.e., shop or service credit (Gift Cards, etc.) or an item exchange, etc. Doing so could possibly prevent the customer or buyer from filing a complaint against you.
If all else fails, you have the option to take legal action against the individual (theft of service, etc.) but, you have to have proof meaning documentation and/or facts which takes your time and money. Bottom line, is it worth it ?
Just some thoughts from past experiences of course as there's no perfect solution. The good news is there are many more honest customers or buyers out there than not so honest customers or buyers.
All the best,
jk
