Unknown source of suspicious billing

I've received several alerts and don't know what to do about them. They're old and I am, too. I have health problems that have hospitalized me several times in the last year. I caught an ID theft years ago that showed they had everything they needed to open accounts. I fortunately put a freeze on them before they could do any significant damage. The bank reimbursed a $100 + charge.

Now I have a bill, though, that none of my health providers know anything about. It's for about $1,200. I found out from both my insurance agent and a credit report. It's hurting my credit and I don't even know who's billing it. 

It's incredible that the one platform we are trusting to keep us safe is riddled with spam emails claiming our accounts are expiring and need to be renewed. The giveaway that it's spam is the email address it's coming from. Nothing indicates that the message is coming from Norton. NEVER EVER click on a link in the email.  Sign into your Norton account on a fresh Internet page with your username & password. On my account online it shows that I still have several months before I need to renew so that also told me these were spam/fishing attempts to get your personal data.

Do you have a physical paper bill? That should have information about who wants the money.

If not, how did you find out about this bill?