After doing the job he demanded a large payment

Praise be to Allah.

If this man is a professional and does this work for you and others, then he is entitled to the usual payment, and he is not entitled to any more than that. But if he is not doing this work on a regular basis, then you should come to some agreement with him. This should be a lesson for you in dealing with people, not to deal with anyone until you know what you have agreed to.