when i lived in texas at a an apartment complex i got a transfer from my employer, gave my 30-day notice and knew i was forfeiting my 450.00 deposit and the apartment was rented two weeks after i moved out and now the complex is wanting me to pay all the months left on the lease. what can i do?

Read your lease. The lease is the primary determiner of notice and if that is not there, then you should consult state law for the type of lease you have.