Dear Felix
I’m writing to thank you for [PRODUCT/SERVICE, ex. procuring our cleaning and disposal services]. It is our pleasure to serve you!
I’m confident you are happy with [BENEFIT (S) OF PRODUCT/SERVICE the cleanliness of your premises] and I hope you keep us in mind for all your future [NEED, ex. cleaning and disposal needs]. I want you to know that you can call me at XXX-XX-XX if there is anything I can do for you.
Thanks for your business.
Regards
Lydia