Some 30 million people across the nation are receiving notices that they may be eligible for $25 or more from the settlement of a class action suit over foreign currency conversions on credit and debit cards.

The case alleged that card companies overcharged when converting foreign transactions into dollars and didn’t disclose all fees. It looked at currency conversion fees — often up to 3 percent of the transaction value — on credit card and debit card as well as cards used to tap automated teller machines.