Prefix currency on Numbers 11.1

Every time I open an Excel file in Numbers 11.1 the prefix currency is set to US dollars. But since I work in Mexico, I need the prefix currency set to MXN Pesos. I have to do it manually. And sometimes there's so many cells, that occasionally I miss one or two. How can I permanently change the prefix currency to Mexican Pesos?

I have already changed the the settings in System Preferences>Language & Region>Advanced>Currency to Mexican Peso. But I still get the USD currency every time I open an Excel file in Numbers.

Anyone has any suggestions? Thanks