My parents think I'm stealing money from their debit card?

They got a letter saying that the card was shut off because of purchases that weren’t made by them.

They called me down to look at the transaction record and asked me if I made any of them. I’m the only kid so I’m the only one that would have access to the card.

But I didn’t. I have my own debit card and the charges were made to a web hosting site which is something I wouldn’t have any business in.

I explained to them that all of my accounts (itunes, zappos, amazon, etc.) are set up with my debit card and I check it every time. I offered to show them my transaction list but they said no.

I went back to my room and remembered that back in January my stepmom’s computer got a “virus” and she was forced to pay for this fishy virus protection software that wouldn’t let her close out until she paid for it (with that debit card).

I remembered it was the debit card because she doesn’t use it and said that she didn’t care if it was a scam because there’s only a limited amount of money on that card anyway. When she cancelled the virus software it was very unprofessional.
She just called and complained and the guy said “okay” and the money was wired back to her account. But they still had the card information. So I reminded her of that, but she didn’t seem convinced.

And now I’m worried that by bringing that up, I’ve dug my own grave by seeming like I’m trying to get out of trouble.

So what can I do? I feel like I’m being accused of something I didn’t do! I would NEVER steal money from my parents.