Debit order information

I called in to change the bank details on my vehicle's finance debit order, which should be a very simple process of inputting the new number. But instead I am told I need to send through a signed letter stating I want to change my bank details. Please explain how this is supposed to be possible if I do not have a printer and all internet cafes are closed due to the lock down. And then the agent says they probably won't get to it before my deduction date on the 25th. I can guarantee that if you don't get your money you will be very fast to contact me but when I need assistance, none is offered.