Seeking Advice

I am currently living in the H Apartment at Moa Island in Gyeongnam.
I am asking for advice regarding a noise complaint issue from the neighbor downstairs.
It seems they have a baby, which should be a blessing in this era of low birth rates.
Because of that, they filed a complaint asking us to refrain from using the master bedroom bathroom at night because the baby cannot sleep. Now, they are claiming that it is too noisy at 10:00 AM and that the sound of footsteps is preventing the baby from sleeping.
During the day, it is just my wife alone in our home; only two of us reside here.
If they were complaining about nighttime noise, I would fully empathize and be careful, but I am getting angry because these complaints are becoming excessive.