This just happened to me not too long ago on my 2006 wrx. According to the dealership this is a common occurrence with the 4pot calipers
Only the fronts, the back 2pots do not have the issue. I just used tons of PB and cranked the wheel all the way so I was able to get a small pipe on the end of my wrench. Just a tip, use a 6 point wrench if you can, the bolts are extremely soft for some reason and a 12 point may murder the head. I ended up braking the bolts on the driver's side and had to attempt to pound the caliper away from the mounting bracket which lead to me braking the caliper
I reinstalled the bolts with some anti-seize in hopes that this would not happen again and torqued to specs. Good luck with yours! hope it goes much better than it did for me haha.