How to go about fighting this MIP?

I was stopped driving home at around 4 in the morning when I was stopped by a police officer. I was asked to get out of the car and handcuffed. I asked numerously for a breathalyser test, or for blood work to be done, yet the officer refused stating that I would only be charger with a PI (Public Intoxication) which did not require him to give me any sort of sobriety test. After being released from jail, I found that I was charged with with MIP. Any advice if I should fight this, or should I just accept the punishment for something I didn't do.