Best you will never stop people like that though. But charging for diagnosis gets rid of this no fix no fee that people seem to think everybody does.
If the boiler is shot to pieces I say I will take the diagnosis fee off the price of a new boiler. And I promise I don't add it on before I take it off. Honestly.
If the boiler is shot to pieces I say I will take the diagnosis fee off the price of a new boiler. And I promise I don't add it on before I take it off. Honestly.