Answer: (I tried)
Dear Jane Doe, CEO
Greetings and good afternoon, I want to thank you for providing me with the service I required; your employees got right to work and wasted no time. During our partnership, the product and service have really profited us. I am thrilled to collaborate with you in the future. If you recall, our agreement stated that you would provide us 30% of the proceeds from the sale of your goods. We'd want to thank you for helping to grow our company. Thank you so much, and have a pleasant weekend.
Sincerely,
(Insert your name here)