Your doctor has also told you to increase the Metformin. Do you agree with this? Doctors are not gods. They do not know it all.
At the end of the day, all doctors are supposed to do is advise, with reasons. They cannot tell you to do anything. The choice is yours, and yours alone.
In my opinion, and I am not alone in this, the finger prick readings from blood glucose meters are far more an accurate indication of how your blood sugars are than the HbA1c. They tell you instantly what each meal has done to your levels if you test before you eat and 2 hours after first bite. If the rise is too high you can change that meal to something less carby, right there and then, without waiting months for your next HbA1c test. Most GPs tell us not to test, and give a variety of excuses, but this is for financial reasons. If they told us to test they would be obliged to provide the mean to do it - and they can't do this because of the costs involved. Bite the bullet, ignore the GP, and buy your own meter. That is the only sensible thing to do.