Service Charges Dispute - Respond to Letter

I own a Leasehold studio flat &
I have received a Service Charges demand/claim from the solicitors of the Managing Agent.

The amount being claimed is outrageously , excessively high & the Solicitors have added Legal Costs to the Service Charges.

I have paid in protest the previous service charge (due to very poor repairs etc) and the service charge for the remainder of the year is due again.

The Agents solicitors have wrote to me on a without prejudice basis looking to settle pre-court action & I need to respond before October 9th(see attached).