I am having trouble with Medicare trying to recover money. Where can I get help?

July - The auto accident.....was there a settlement paid to you?
Like an $$ award above the medical costs paid by your health insurer back in 2007 -2009. If so, you might be dealing with recovery due to Medicare Secondary Payor Act. I think Act was signed in back in 2012 or maybe 2013 & retro'd back 5 years. Award $ can be recouped if Medicare pays for care arising from follow up due to the accident that settlement $ given for.
If there was a settlement, I'd contact your old personal injury atty to help you figure out if thus is the issue & sort this out.

If the appeal period hasn't expired, file an appeal with Medicare, based on the notices they sent rejecting the charges.

Speak with an attorney.

The only way Medicare would have a record of these charges is that the doctor's office billed through them. You may want to contact the doctor who has done the billing and ask why they billed Medicare.

Yes, I would take your documents to your Social Security office which will tell the computer at Medicare the exact dates you were enrolled. Also, ask to talk to a supervisor. You might be able to make an appointment where you live to cut down on wait time. Call Medicare on the phone, write letters with documents, and leave no stone unturned until someone corrects their mistake.

I totally sympathize with you. Medicare is very vigilant about injury status! I was on Medicare already when I had a car accident related injury in February. My auto insurer became my primary insurer covering all expenses until the proceeds became exhausted In June. I received a letter stating this, and I sent a copy to the BCRC (Benefit Recovery Coordination Center) so that Medicare would revert back to being my primary Insurer. That was five months ago, and my case is still open. Every month or so, I call back, and they go over my documentation, say the case will be closed, but it is not.
I hope many others with Medicare related issues post their advice for you, and it might help me too. Maybe I'll bring the documents myself in person to a SS office, as already suggested -

Send them copies of the documents proving the dates. You may have to bring those original documents to the SS office.