1. Have a careful review of your policy to nake sure if your car in insured on Actual Cash Value basis, which I believe is, because your car is obviously an old or second-hand. In this case, depreciation must be considered in loss payment to reflect its market value. Apprently your insurer believe your car it's cheaper to pay cash than repair your car. You got only $2,170 because they believe this is the so called "fair market value".
2. They shall not charge premium after the payment. In your case the car is totaled, in other words, he insured object no longer exists after they paid the loss and took away your car. The contract between you and your insurer was over at that moment. You are entitled to get your money back.
3. Monnex is not an insurance company. Purely a broker. Make sure you know what you will get from them before you pay.