The Grammar Doctor

Q.Please help me settle a debate. We are putting together a handbook, in which there is a list of contact names. The heading for this section is "Whom To Call". I believe it should be "Who To Call". I believe "who" is the subject in this case, as in "Rebecca is the person to call". I can see an argument for "whom" if "you" is the implied subject and "Rebecca" is the object (Whom should you call?).
Which is correct?

A. "Who/whom to call" is not a complete sentence, so there is no subject here. However, a pronoun before an infinitive (like "to call") should be in the objective form, so the correct heading is "Whom to call"