I am a different contributor. The problem that you may be running into with your lender here is that the escrow account is often (but not always) part of your larger mortgage contract. The funds in the account do not just cover your homeowners insurance, they usually cover real estate taxes, flood insurance, and any other large dollar figure payments associated with keeping the property clear of liens and protecting the mutual investment.
If your lender is claiming they have a right to keep the escrow fees as established, you can ask them to point you to the part of your contract dealing with this fee and why it cannot be modified (some loans carry an "impound escrow" which is non-negotiable and the homeowner must continue to pay fees regardless of the balance of the loan, or the value of the equity, while others have "minimum escrows" which may be more variable, such as when you take on your own insurance).
As with all contract questions, the best source of information is the mortgage contract itself, there will be a section or clause relating to the escrow account and tell you what terms you are required to keep and if you can replace the account payments through a purchase of your own insurance.
While I do hope that your contract allows for the modifications and that this specific clause of the contract only needs to be brought to the lender's attention, if not, I hope that you can reach a reasonable resolution with your lender.
If you have any questions please do not hesitate to ask.