Welcome to the Community @Blondie
The short answer is yes it is. What you have described falls into the category of a ‘change of mind’ and a seller can set whatever terms and conditions they wish, including no exchanges or refunds.
If they give a refund you have done better than other members who have had similar experiences who have ordered ill fitting or otherwise unacceptable clothing and have been refused any recompense.
You can find similar examples using the Community search such as
That is their business decision.
When buying online, especially clothing, it is important to read the T&C in detail and be very careful about what one orders. I regularly use ECCO shoes as a gold standard of what one should look for.
