There is no parameter to disable currency conversion updating as far as I am aware. It does this to remain up to date with current conversion rates. We also currently don't have an interface available to add custom currency conversion rates. To do this you'll unfortunately need to add them directly to your database table _cbsubs_currencies.
You can change what currency CBSubs uses by adjusting the "Currency and Price display" parameters within CBSubs > Settings > Global.
Please take no offense, but could you please stop typing in all caps? We do not appreciate being yelled at as is perceived by most as yelling. We're here to help.