How to deal with poor service?

I have not been refunded my full amount. I was sent a small portion of the total coast. the reason for the full refund is for not resolving the concern and being dragged along. I empaled the owner after months of not sending me information were to send to have repaired due to him rushing building the product (by his own admission). He stated to keep the product and he would refund me in full.

I have received less about 10% of what i paid and still have a product that has the problems when I received it. I have not used the product as I want to have it fixed then lead to having it returned and getting a full refund. I did not want to inconvenience the company with a used product that they would fix and sell as used.