commercial insurance

I need to cancel my policy number because the insurance company set a monthly fee for $70.00per month, for one year. however that was not my fault that they did not withdraw maney from my account on the followed months. Three month later, they sent me all prove of insurance, but this time it says $105.00 per month. I do not understand why initially was set-up for $70.00 and now $105.00 per month for one year!. Now I want to cancel it and have to pay penalty.which means I still owe money to the insurance company. What would you suggest for me to do other than writing them a cancellation letter? Thank you.