You can hail a taxi off the street or pick one up at the many taxi ranks throughout the cities and towns - or simply phone for one yourself. You are free to choose the taxi company you want to use, you do not have to choose the car that is first in line at the rank.
All taxis in Norway accept the most common credit cards such as VISA, American Express, Diners Club, Eurocard and MasterCard. You should inform the driver at the start of the trip that payment will be done with a credit card.