Where can complain about increase of my auto insurance premium?

Answers: Your state should have an insurance ombudsman. Check your yellow page under state government. You could probably also complain to your agent, that's what they're in that for.
The department of insurance in your state. But keep contained by mind they can raise your rates for any reason. Mostly it will be a state wide open increase due to high volume of claims they had to taken on during the year.
Also, the DOI will solely deal with LEGIT complaints.."unpromising faith" if the increase was legit then a moment ago switch companies.
Your insurance company. The way to complain effectively is to leave them and jump to a cheaper insurance company.

Follow the money
you really cant but you can look for a new company and get rid of the mature one.

Related Questions:
How to much to ask for on an auto insurance settlement?   Why would auto insurance budge up in recent times because of a divorce?   When getting your vehicle inspected do they appointment your auto insurance company?   I reward $ 88 monthly for my auto insurance. Is that too much?   Can I buy a vehicle and hold the title contained by my moniker and still be covered underneath my father's auto insurance?