Your application is reviewed before being accepted/rejected, there's no point in ringing them again once a decision has been made.
However, they review your application meaning if you're good enough all-round and show exceptional capabilities, not necessarily in the academic verse, relating to your subject of choice (i.e significant contributions), then they may well accept you even if you don't quite have the grades, they may be slightly more lenient (depending on uni and degree of choice) as it's only 1 grade down and it's 1 subject, and isn't the most relevant subject for the degree.
But don't call them again if they reject you already, that's wasting valuable clearing time.