I requested prime precessing after I-140 pending for 3 months. I had to send
I-907 twice before it actually happened. The first time, I sent the form as
regular first class mail. One week after I mailed the form, a guy from
Florida called me saying that USCIS had mistakenly "sent" my I-907 form to
him! Had he not informed me, I would have been waiting for who knows how
long. Then I immediately resent the form by USPS express mail and my case
status changed the next day!
Not trying to scare you, but I think you should call the custom service
number (maybe the number on the I-907 instruction?). A week is long.