How to contact first national bank? First Interstate Bank Credit Card toll free customer service number : +1-888-752-3332, +1-307-684-2581.What is first bank customer care number? CONTACT FIRST NATIONAL BANK. The main phone number for First National Bank is 608-486-2386. The assigned Federal Reserve Office for First National Bank is Fed 091000080.What is the phone number for first national bank? The address of First National Bank is 1600 East Bridge Street, Brighton, Colorado, U.S..