Yep it happened to me once with my GP.
Basically at the time I was prescribed a medication to treat addiction and what sucks with that stuff is that you tend to get addicted to it (how ironic).
So I was always early every time I needed a new prescription because I took more than I should have. To block this, my GP made those special prescriptions which only allowed the pharmacy to give me one week's worth of the drug (up until that point I had regular monthly prescriptions).
As you can imagine I wasn't to pleased with that arrangement so I managed to scam the pharmacy into giving me the whole month at once. To cut a long story short I got busted by my doctor and she said that she couldn't have me as a patient anymore.