Double debit order.

What a way to ruin my holiday. I only get paid on the 20th of each month which I made very clear when I signed my contract at Lemon Tree Apartments. I received a text to say my Debit Order will run from the 15th. I called the finance office to state that I only get paid on the 20th of each month and won't have sufficient funds for rent on the 15th. I was told that it's fine and the debit order will just go off from the 15th to the 20th. To my dismay they have now taken off double my rent. I can't travel as the offices are closed and my bank cannot reverse the money. I also did not authorize for two debit orders to be done. I feel like death. How will I support my family?? You have ruined everything during a season that's meant to be joyous.