Suggestion over the cancellation request by the buyer

I have been working on an order. The buyer has asked for modification everytime, I delivered the project. I have made all the corrections for his satisfaction. Not only this, there were three additional articles which as the matter of fact, was not at all the part of the deal. But since I am always going limitless to satisfy my clients, so I even got agreed to create those additional contents as well. However, my frustration level shot up, when he recently requested for the cancellation refund.
So, if anybody who has gone through the same experience, kindly help me on how to handle the situation. Shall I offer him the refund or raise a dispute. I really need your suggestions and help in resolving this issue. I need your suggestions ASAP... I hope you understand

Many Regards
Ryan