Calla, like the flower?I don't think Callie does or even should work on its own. Cali doesn't happen where I live, so it just looks odd to me. And I can't see the point of having Callista moult an L. Calliope is too noisy to be a name.
I can't make sense of Calista. Especially when the Greek original clearly has LL. But it's not used as a name where I live, or I've certainly never seen it, so what do I know?