by use of 1 or more interstate telephone calls initiated either by a person who is conducting the plan, program, promotion, or campaign or by a prospective purchaser or contest or sweepstakes participant or charitable contributor, or donor; but
if the person making the solicitation does not solicit customers by telephone but only receives calls initiated by customers in response to the catalog and during those calls takes orders without further solicitation.
shall be imprisoned for a term of up to 10 years in addition to any term of imprisonment imposed under any of those sections, respectively.