The phrase "again called upon to" is correct and usable in written English.
It can be used when referring to a situation where someone is being asked to perform a task or duty once more.
Example: "After successfully leading the project last year, she was again called upon to take charge of the new initiative."
Alternatives: "once more requested to" or "repeatedly asked to".
Less than a week after their return, Battleship Division Nine was once again called upon to protect the Scandinavian Convoy as part of a general Grand Fleet response to intelligence reports suggesting German battlecruisers were loose in the North Sea.
The Northwestern University law professor Steve Lubet said: "There would definitely be calls for her recusal in a rerun of Bush v Gore," if the court were once again called upon to decide the results of a presidential election.
Addicts of wigs-and-breeches television serials adapted from doorstop-size British novels may well delight in this production, in which the classic elements of story-theater are once again called upon to streamline a narrative that spans hundreds of pages of prose.
Early on Drogba headed against his own crossbar from a corner, with Krul again called upon to rescue his side as Ramires immediately broke down the other end.
They continued to enjoy the better of the play at the start of the second period, with Lonergan again called upon to deny Butterfield from close range.
The Kansas offense failed to gain a second first down after the interception, however, and kicker Scott Webb was again called upon to attempt a field goal, this time from 32 yards away.
Again, the notion of solidarity is called upon to create cohesion and order in our twenty-first century superdiverse urban societies.
Mr. Bush once again called upon the Senate to pass a bill central to his "compassionate conservative" agenda that would make it easier for religious groups other than giant institutions like Catholic Charities to apply for federal money.
In a statement after the meeting, the group "emphasized that there can be no military solution to the Afghan conflict and again called upon the warring parties to agree to a cease-fire and enter into negotiations aimed at bringing about a political solution to the conflict".
Before giving notice of his recall, the Bulgarian Minister again called upon the Greek government to order the cessation of hostilities and protested against the capture of the Bulgarian detachment at Salonica.
Well-known general concepts of soil behavior and general chemical categories (solubility, molecular size, and functionalization) were again called upon, but were related to an ever ambiguous notation of "organic matter".
