1999 Toyota Camry automechanic replaced transmission with n

Transmission problem
1999 Toyota Camry 4 cyl Automatic 200000 miles

i got my transmission replaced, afterwards the speedometer as well as the acceleration was erratic. They inputed some kind of a diagnostic sensor and it read that the problem was the speed sensor.

i went to another mechanic for a second opinion and he said that the transmission was leaking oil and that the transmission itself wasn't even that of a toyota brand. At this time i;m not quite certain if he's telling the truth.

i got the original mechanic to give me a manufacturers warranty, however, I would rather not pay addition bucks for labor for replacing this transmission once again. Isn't there a law against such mal-practice, how can I make sure that these people get the punishment that they deserve?