Mitigating circumstances

If you miss your conditional offer grades and are rejected by the University; is it still worth calling them with details of mitigating circumstances that they might reconsider you, or is that time now passed and would need to look for either different course, or different Uni?

i.e. Once they have made up their mind in UCAS hub, there is no change possible to this?

(And fingers crossed this is a moot point!!)

Thanks!