Why Would Your Doctor Cancel You As A Patient When

Why would your doctor cancel you as a patient when you are urine tested? My test came out negative for Percocet when I take a controlled amount as prescribed by my doctor each day. I take 3 Percocet a day, one every 8 hours as needed for back pain. I also am seen by the doctor for diabetes, pancreatitis, heart/ Afib, high blood pressure and high lipids and cholesterol. I was just told I cannot return to the clinic where my wife and I have gone for three years. Please help us to understand this problem. Fred email at YYYY@YYYY