Airport Car Hire

I've booked a car from Airport Car Hire starting from Bergen. I wonder if this online company is reliable or not. They did not ask me for a credit card number (or i forgot if I had keyed in any details) but they have confirmed my booking, giving me all confirmation numbers etc. Tried to call Avis Norway to confirm but it seemed the line could never be put through. Just don't want to arrive Bergen and find that the booking is not valid. Has anybody used this online Company before? The price is about 20% less than the Avis.