The Second Circuit has noted that "[t]here is a circuit split on the question of whether the actual use [of the telephone] by the defendant must be an interstate one" for such acts to be covered by 18 U.S.C. 1958. The District Court had answered that question in the negative, in accord with decisions of the Fifth and Seventh Circuits. The Sixth Circuit has taken the opposite view, as had two district courts in the Second Circuit. The Second Circuit agreed with the Fifth and Seventh Circuits.
In that the Sixth Circuit decision was limited to its facts by a later Sixth Circuit opinion, it is unlikely that this issue is likely to go up to the Supreme Court at this time.
The decision in United States v. Perez
can be found here