What will happen if i return a used car i've only had for 2 weeks.?

my dad bought me a 2006 scion xb, but it actually came out to be too much money for us to pay. we planned on returning it the second day we had it but the dealership said no. if we fight to return it what will happen? can we do it? will it affect my dad and my credit score? we have only had if for 2 weeks, the first payment hasn't even arrived yet.