The National Bank does not exchange foreign currency.
Former national banknotes and coins issued by euro area countries can in most cases still be exchanged for euro. This is done only by the national central banks. For more information, please refer to the ECB website: Exchanging national cash: addresses and time limits.
To exchange old banknotes and coins issued by countries that are not part of the euro area the Central Banks concerned or possibly a bureau de change should be contacted.