If you have landed on this article, than you already know that you can not disable the currency conversion in Google Merchant. You will notice it is grayed out. There is actually no way of disabling it, no need to worry!
Why does it not matter?
When you have created the first data feed with currency conversion, you might remember that you have chosen your native currency rather than the target country currency. When choosing your native currency for a foreign target country, than currency conversion is automatically enabled if it the feature is enabled in the first place.
To check if it is enabled, please login to Google Merchant and go to Shopping Ads > Configuration
If you have changed your might and wanted to use a dedicated data feed for the foreign target country, all you need to do is choose the target country official currency, rather than a different one.