While I am a huge proponent of using lifestyle changes, I am sorry but with an A1C of 12.4, insulin is appropriate. You can easily slip into diabetic keto acidosis at that level, which kills within days if you don't make it to ICU.
However, I agree strongly Dr should have called you directly. You need a lot of help getting started with all these changes. Shame on him.

So glad you have already been able to get your blood sugar down so quickly- that's great! Just remember, most people don't change overnight like you did- that is why your dr said to use insulin. As high as you were, it is imminent life or death situation.....