The plumber did not correct the problem and was called back on the same day and billed me for two separate calls. Is this legal?

If the plumber had to come back to correct a problem as a result of his initial work, and charged me for a second visit, I would be outraged! While I am no lawyer, I believe it would not only be poor business ethics, but I believe illegal also. Either way, at the risk of sounding inappropriate, it would be all out war on this company. I would also contact the Better Business Bureau and lodge a complaint.