I locked in 0% for 72 months when I ordered from Mark Dodge and took delivery in June. My credit score is 800+.
So, yeah, you got screwed and lied to by the finance guy. Happens all the time. In my experience (MD being the exception), the finance guys are the least scrupulous people in the dealership.
The good news is, you can refinance, not for 0%, but for around 2%.
The finance guy may have told you you need to wait 3 or 6 months or whatever to refinance. Read over your paperwork, but if he did tell you that, it’s probably another lie. What he means is, he and the dealership don’t get their kickback if you don’t wait that long.
If it were me, and I had a bad experience with the finance department and felt they were dishonest, I’d refinance right away. In fact, a few vehicle purchases ago, I got the same BS you faced, and I refinance the minute I got home. I didn’t make a single payment to the dealership’s chosen bank, and the dealership presumably didn’t receive a dime, either.
On the other hand, if you felt the finance department was fair and honest, maybe you’d do them a favor and wait. But it doesn’t sound like that was your experience. Screw ‘em!