How to change refund policy

I don’t believe you can. Standard products will in the main fall under Amazon providing prepaid return labels. You can exempt items from triggering a prepaid label - though this is for goods over £100 only. I don’t think that would exempt them however from actually being exempt from returns full stop.

There are some exceptions here however earrings don’t appear to be one. There is a section referring to items classified as hygienic by amazon - again though, items in Jewellery don’t seem to apply.