Can I Record Blue Yeti Mic & iPhone Callers Simultaneously in GarageBand?

Hello Podcasters! Just starting a podcast, however – techno snags! In GarageBand, would like to hook-up: Blue Yeti Mic (Trk 1); record callers from iPhone (Trk 2) – do a simultaneous recording. Is there an audio interface I need for iPhone while Blue Yeti is plugged into MAC ??