You could write the client that they are valued for their loyalty and are therefore going to be rewarded. Maybe something like if they have 1 extra clean in the next 3 months that it will be only half price. People are generally in a rush for a bargain This way you gain, not loose money, then add on the small detail at the bottom of the letter that from such and such date the prices must increase due to a rise in the price of some product or other. ( If people have reason for price increase they accept it, even if it's a reason they don't understand) Hope this helps...