Japanese is all Greek to me , but I have often wondered why, if "onegai shimasu" is supposed to be a formal statement in this context, should not "onegai shimashita" be used? My limited training has imparted that the "-masu" verbs are informal, and the "-mashita" verbs are formal. (Of course, I have also learned that there are seemingly infinite exceptions to this type of grammatical "rule". I think I'll stick to English. I have a hard enough time with that.