We had kind of simmilar experiance requesting an interview change.
My wife is from China but was a perm resident of Japan at the time. She lived and worked in Japan and took a temp assignment in China at the time of the I-130 filing. We requested Japan however, Per USCIS, she was resinding in China at the time so her case was assigned to Shanghai. After geeting the run around from USCIS, NVC, and Shanghai consulate we had to get our State Rep's and Senator's office involved. Eventually we were able to get our case transfered to Japan.
TLDR: you'll get the run arround trying to transfer your case. If you hit a wall you'll probably need to get your State Reps involved. I got my House and Senate Rep's offic einvolved. It was pretty easy to contact and they usually have staff to assist with immigration problems. If you're from a larger state it might be a little different.