How Long Do You Have to Wait to Have Implants Exchanged for a Smaller Size?

I recently had breast augmentation with 400cc silicone highprofile implants under the muscle one month ago. I am very unhappy with my results, I am 49yrs old, 125lbs and my old bra size was 36A. I wanted to be a small C but now I feel huge. I had originally wanted 325/350 but with being excited to finally have this done and recommendations that going under muscle would reduce size 20% I ended up choosing 400cc and now really regret it.