If you're a UTLA member, you should be on the phone to them.
However, even with the union contract, you've pretty much got nothing. The district has pretty free reign under the contract to make transfers such that their "best interests" are served, as long as they don't change your classification, especially if they abolish the position as being overstaffed.
You should read your contract or have the union help you understand it. There are mediations available to you though I'm not seeing anything at the face of things that makes this transfer invalid.

