What investigation takes place when you report fraudulent activity on your debit card?

So I log into my BofA account today to find an $8 charge from Netflix, which caused me an overdraft. I don’t have a Netflix account, and never have. After speaking with a representative she tells me that this charge has occurred for the last 5 months straight. We eventually got Netflix on the line and found that I indeed did not have an account with them, but that my card was registered in one of their accounts. Netflix said they would do an investigation and get back to me once they worked things out.

I have a sneaking suspicion that my ex-SOB-roommate is behind all this. At some point or another he probably used my card to pay for a month of Netflix, and then just left my card active on his account. Regardless of how much I hate this guy (and believe me, I REALLY rightfully do at the moment) I’m not looking to cause more waves between us (especially now that he’s finally gone and out of my life). That’s not to say I don’t want my $70 back of course. I just want it back without a big scene.

What does the “investigation”, which the Netflix rep. spoke of, entail? IF it is my ex-roommate, what will happen to him as a result of this?