Debit order doubled in one month without my concern

I made arrangements with VW finance with regards to arrears i have on my Vehicle. 27/11 I managed to pay my monthly instalment ,with an agreement that i will pay another amount to reduce arrears in 3 months starting from the 29/11. they attempted to get another money on 28/11 which failed because there was no funds.They again came back this morning 29/11 to take another money which they took normal instalment plus the amount which we agreed on to cover my arreas.I am sitting with no money now due to 3 payments they received from me.

I need refund for the money i paid on the 27/11 Via debit card transaction then i have paid Nov instalment Via debit order plus an amount to cover arrears. Please assist.