Double payment

My payment date Is on 25th for December we received our salaries late on the 31st to my surprise now when I want to make a payment I'm being told that it's gonna be R1289 when I ask why they are telling me that am paying for January too. What I don't understand is that I've never agreed to that arrangement and no has called me to notify that payments for January would be paid earlier. Where are gonna get the money to pay upfront. Rain is not fair to it's customers