Question regarding registration for those who have sold a house

I am currently living in a house with a Bogeumjari Loan from the Korea Housing Finance Corporation (HF).
I am selling the house as I am moving this time.
I am supposed to receive the balance, repay the loan to HF, and then cancel the collateral mortgage.
Since HF does not handle the cancellation registration themselves, they told me I must do it myself, through the handling bank, or via a judicial scrivener.
However, I am in a rush because after selling, I have to go to another real estate office on the same day to purchase a new home.
I won't have time to visit the bank to process the registration,
so would it be possible to pay the service fee and registration costs to the judicial scrivener brought by the buyer??
I have never seen someone hire a judicial scrivener just to sell a property before...
I thought that paying a certain fee to a financial corporation would include the cancellation registration, but apparently they don't do it. What should I do??