Is this a Mortgage bait and switch tactic? What should I do?

[Charles Wang]

Hi Everyone! I've come here to get your advice on something. Two weeks ago, my offer was accepted for a duplex.  I decided to get a loan from a major US bank and got in contact with one of their loan agents. I emailed him the purchase contract and my pay stub etc.. He calls back and says he can lock me in for a rate of 4.375%. I accepted and he started the loan process. Next, the disclosures come in the mail and everything looks good. It had the correct property address, stated it was a 2 unit and has the box checked saying "yes",  my rate is locked in at 4.375%. 

Two weeks later (today), I get a notice saying my loan has been conditionally approved. Shortly after, my loan agent calls me and says, because the appraisal came back as a duplex, he can no longer offer me the original rate. Instead, I now have to go with 4.65%. I was totally shocked by this! When I asked him why, he said when he locked the rate,  I told him I was buying a single family home instead of a duplex. That makes no sense to me at all! I specifically told him I am buying a duplex. Furthermore, the purchase contract I sent him and the disclosures all said it was a 2 unit duplex. He had to put in the address of the two units to lock in my rate. How could he not have known at that time? His statement makes no sense to me. When I told him that he was not making sense, he started to yell at me and said that I don't understand the process and my rate can change even if I locked it in.

Is this a bait and switch tactic? What should I do about this? I am very close to closing. Any advice?