If you haven’t cut the pattern out, usually fabric stores allow you to exchange it. If you already started cutting out the size 22, if I were you, I would just move forward in creating your muslin. I’m not concerned that it won’t fit you in the bustline but there could be a possibility that the shoulder area may be a little too big. You won’t know for sure until you can try on the muslin though. Just use some cheap muslin fabric and baste the pieces together enough so you can try on the basic bodice shell. If you need to take in a little here and there, mark with a fabric pen and then transfer those marks to your pattern so when you use nicer fabric, those adjustments have already been made for you. You can do it! 🙂