Call on verb – Have recourse to or make an appeal or request for help or information to. Tell and call on are semantically related in demand topic. In some cases you can use "Tell" instead a verb "Call on".
Tell verb – To give an oral or written account of in some detail. Call on and tell are semantically related in instruct topic. Sometimes you can use "Call on" instead a verb "Tell". Nearby Words: telling, teller
In Horrible Histories, none of the courtiers, for obvious reasons, want to tell Henry VIII his wife is unfaithful, so they call on the court jester to deliver the news.
Another occurs when Baum interrupts the keynote address at an investors' convention to tell him that that there is a zero percent chance that things will not get worse, then gets interrupted by a call on his cell phone and walks out before the speaker can respond.