Missionaries often tell me that Jesus preached only Torah true Judaism and never contradicted the Jewish Bible.

Oh really?

The Jewish Bible in Deut 24 says very clearly that a husband and wife are allowed to divorce, and after which, the woman is allowed to remarry.

In Mark 10, Jesus says that this is actually not allowed and that
a) a couple is not allowed to divorce (Mark 10:9)
b) a woman who remarries after divorce is committing adultery (Mark 10:12).

So if you really believe in the Jewish Bible, and you really believe that a true prophet cannot change what the Torah says, you would agree that Jesus is a false prophet.