What steps to take without written contract?

My company installed 10k worth of equipment for a customer. He paid the equipment fees up front with intent to pay labor once job was completed. Finished work May of 2022. Cx was on honeymoon and was supposed to make contact with ke after they returned. Cx total labor invoice with discounts was $3300+. When he made contact with me after 3 weeks, he informed me he has had other contractors come and inspect my work to which they gave a much lower price. Now customer doesn't want to pay for my services or finishing materials on-site and installed. He did pay $200 to which I told him I would take it off the total he owes. So current balance is $3100+.