I'm so upset right now! (NWR)

FH and I are supposed to close on our first house tomorrow. We are so excited, but today we got a phone call from our mortgage lender, and we are starting to feel like we are being taken advantage of. The lender is trying to tell us that our interest rate will be about .5 % higher than what was stated in our Mortgage Commitment. This is very annoying and upsetting for us since it means quite a bit of extra $ each month for our mortgage payments. We are especially annoyed because the lender said it was because of what sounds like a paperwork error on their end that was not our fault. And they waited until the day before closing to tell us, so now we can't even go and try to get a mortgage elsewhere! I called our real estate attorney and she said she'd try to fight it since she said it looks like they are going against what they agreed to in the mortgage committment. FH and I are so upset and anxious right now waiting to find out if we will have to pay the extra money. Instead we should be excited about getting our first house, but this $h!t is ruining it!