When I shoped I was happy for the good deal. Howev...

When I shoped I was happy for the good deal. However I was given two interest rates which is for 60 months 4.9% and 72 months 3.8%. After deal complete i took the car home. And few days later I received a letter from the Bank telling 4.9% for 72months. By seeing that I lost the trust on your dealer ship. I know its business however need to to fair, now i need to waste my time to run behind all these.