If a person A, speaking by telephone to an election official B in Georgia, attempts to influence that official to improperly alter an election result in a way that would constitute frauds or otherwise be a violation of Georgia law, then the person A has committed a crime in Georgia. There are various ways to commit a crime in a place without being physically present in that state.
Since there is no question what was said on the telephone call in question (because it was recorded) the question to be determined would seem to be whether it constituted a crime under Georgia law, and whether the Georgia officials think it is worth prosecuting.
It is true that a trial for a criminal accusation is normally held in the state where the crime was committed (or allegedly committed). But that need not be in a state where the person was ever physically present. If a person living in State C does business is state D, and is requires to file a tax return with the authorities in D, and it is alleged that the return was false, then the person is being accused of a crime in D, committed when the false return was received in D.