When Diane ends her call with Will (around 4 minutes in), you can see her phone is upside down. When she's on the phone, you can see the headphone jack near her mouth and when she brings the phone down after hanging up, the charging jack has been near her ear.
On the model of iPhone used in this shot, the headphone jack is still at the top. The original iPhone charger didn't allow much room for a headphone jack at the bottom.