Influx of new work brings new messers!!!!
Thought of sending text along the lines of:
Hi window cleaners.
We last cleaned your windows on such and such a date as you agreed for us to do.
We left details for BACS payment as you requested.
We have texted you with a reminder as normal.
We have left a leaflet reminding you that we have called for payment.
We have called in person (saw you running from the window and hiding in the kitchen)
We have tried calling you but our number seems to be blocked or your phone is permanently off".
As we have received no payment for removing the dirt from your windows please be aware that the next time we are in the area we will be returning the dirt we cleaned off your windows to its original location.