If they charged you more than you owe as per the terms of your contract (an insurance policy is a contract) or based on incorrect facts in the contract (e.g. mischaracterizing your home), they do owe you a refund. They are not legally allowed to keep more money than they are entitled to under the agreement or for the services (the insurance) they provided. If they will not voluntarily repay it, you can sue them for breach of contract, or violating the terms of your agreement. You can sue for as many years back as the "statute of limitations," or time period within which you must start a lawsuit, is in your state for a contract-based case: that is six (6) years, so it appears that you could seek all five years of overpayment. Unfortunately, a lawsuit is the only way to get the money, if they will not voluntarily repay you.