VERY BAD after service generally and for refunds

I bought software through SELLSA and saw just after I purchased it that it was for Windows and not Apple Mac. I immediately let them know having not even downloaded the file. They almost immediately cancelled the purchase but then told me that they do not give refunds on digital downloads. I have yet to find out where this is stated. It was nowhere on my invoice. I have sent countless emails for the refund. All except one email was answered. They simply ignore my emails. I have never come across such bad service. Beware anyone purchasing through them.