Legal Response to deter a client from doing a fraudulent transaction dispute at his bank

I need a deterrent letter to send to a client planning to do a bank chargeback on a transaction where we have already delivered on the products and services paid for. I want this done as quickly as possible today. A client paid money for our service to help him set up a business. We spent a lot of money to pay for Website hosting, website designing of client's website, graphic designing of over 1,000 brochures, design of various PowerPoint presentations, logos, and other stationery on behalf of this client. According to our service terms, we have completely delivered on the services paid for, by this client. There is no question about we having delivered our part of the service agreement between us and the client. The client has acknowledged seeing the website we did for him and later on started claiming that the website is not online, just to try to ask for a refund. Even as I am writing this, the website is still online, but the client continues to claim that the website is not online. There is abundant indisputable proof of everything we have set up for the client available online for any one to see. Most importantly, we have a business licensing agreement that was signed between the client and us via [login to view URL] . THE PROBLEM After setting up the client's business and all the resources we spent money on, to set up, the client wants us to refund the money paid for his business set up. And he is obviously planning to do a bank dispute of the transaction, from the indirect language of his emails. THE ISSUE 1. If I issue a refund, it would not only be absolutely unfair to us, it would be a colossal financial loss to us because we spent almost all the money he paid for her service to set up everything we set up for him. Beside, there is no justification for giving him a refund 2. If I insist on not issuing a refund, he could do a fraudulent credit card charge-back via isr bank because he paid for the service on freelancer.com using credit card. And getting a charge-back is something I don't want to ever experience because of the reputation I want to continue to maintain with freelancer.com payment processor . SOLUTION REQUIRED The option of negotiation with this client is already off the table because this client is so arrogant, abusive even in his emails and resolute in his position of not going forward to use the resources we have set up for him at great expense. Hence, I need a strong an attack-like legal response in the form of a strong letter of warning to deter this client from doing a bank dispute of this transaction because it would be fraudulent for him to do that. If you are an experienced lawyer and knows exactly how to deal with this kind of situation, I'd like you to bid by giving me strong reasons to believe that you know how to deal with this situation and what similar cases you have dealt with for other clients and how it was resolved, and how this could be resolved. If I am impressed with your response and choose to work with you, we are going to be working together for a very long time since every client relationship I enter with all my clients always involve the signing of legal agreement before we start working with any client. I look forward to your bid and detailed response. Thanks for bidding