Stop losing money on variations.
Most variations don't get lost because the customer refuses to pay. They get lost because nobody wrote them down at the moment they were agreed on site, and by the time the invoice goes out the conversation has faded.
The fix is procedural, not personal: the variation is created on the phone before the extra work starts, the customer approves it in their portal with a signature, and the project value changes immediately. When the progress claim is raised it already includes the approved change. No awkward call, no discount to keep the peace.
Variations in the product