If you want to set a base currency for a form different from the global currency, you can do that by following this guide.
1. Edit a Form
2. Hover on the Settings, and then click on Mulit-Currency from the dropdown
3. You will see this screen. Select the Form’s base currency and deselect the Auto currency selection setting.
4. Go to the Form editor and add the currency switcher field
Hide the currency switcher field (optional) #
If you do not want the customer to be able to switch the currency, you can hide the currency switcher field with some custom CSS.
Usually the CSS to hide the currency field is like this:
#gform_5 .gfield--type-multicurrency {
display: none;
}
Replace 5
in #gform_5
with the ID of your form. You can add this code to any of the CSS files in your child theme or to the Customizer.