Out of nearly 60 customers only two have told me not to bother using it on their houses.
Using WFP, I've done over 350 houses per month for four months without one lost customer. I think that the two customers you lost probably didn't want to pay for a window cleaner in the first instance and just used the WFP as an excuse.
I lost a customer in the Summer because she said her PVC door wasn't cleaned properly. After questioning her, she said the windows were spottless. It was just her door! I told her we would pay particular attention to her door next month. She said 'no, I'd rather do them myself'.
I think she just didn't like paying.
Another said to me, 'I'm working now, so I'll not be in to pay you', and after I explained other payment methods she said, 'sorry, I don't want a window cleaner anymore'.
Customers will come up with funny excuses to drop you.
Stick with the WFP and do a good job with it. Soon your customers will just accept it as the norm.
