Legal reply to patent claim infringement email AU/NZ

We own a retail brand in Australia. A competitor to a product we sell filed a very basic and weak utility patent application in Australia and has sent us an email requesting we stop selling our product alleging it violates their patent. They did not title it as a cease and desist. - the patent hasn't been examined - the patent has 3 very weak claims - there is a large volume of prior art that they did not disclose and that cancels out their claims. Claude Opus has investigated and put together an evidence pack and draft reply. We are considering to hire a lawyer to double check and formalise the reply to hopefully close it for good. We want the reply to come from the law firm letterhead/email etc. Please message if interested