Send bank details via email?

I ordered a spare part for my laptop, from Poland. But was not satisfied and sent the part back. Now support writes that I should send them my bank details by email. They have my bank details. Why do you need them again? I wrote to them that I don't want to send it that way but they can't seem to refund me otherwise. Is that normal? Can I do anything about it?

Then you just have to forego repayment, your decision.

I don't see any risk there. I have also sent my IBAN + BIC via email several times without any problems.