NHS debt and Tier 4 visa

I have been visiting the UK to take a few short courses ( On short term student visas) once a year and I would go to my GP to perform some blood tests every now and then. They never charged me as they told me that I am an NHS patient when in fact I am not. I did have an NHS number back in the day when I was a full-time resident/student with a Tier 4.

Now I want to do another degree in the UK and I noticed that any visitor who got an NHS treatment without paying the overdue bills will get his visa rejected.

I don’t know what to do, I’ve been calling the GP and they are telling me that I do not have any bill under my name as I am an NHS patient when I actually am not entitled. When I apply to the tier 4 visa will the immigration officers go look at my NHS records or is it that they will just check if I have any bill overdue? The rules say "relevant bodies must notify the Home Office of outstanding
debts of £500 or more that have been outstanding" but I have no overdue bills as they still consider me an NHS patient, does that mean that the home office will not look at my NHS records?