Letter: Gasoline price fixing?

I recently returned from a raod trip to North Carolina, making multiple gasoline purchases across the southern US this week. Gas prices are consistently much lower (by well over a dollar) in all other states. Additionally, I note prices in the Phoenix Tucson corridor are markedly higher than the rest of the state. Maintenance activities in two refineries cannot in any way account for this. This indicates price fixing at a distributor level unless proven otherwise. I would like to know what steps the Attorney General's to investigate this; and if not, then why not.