Music playing through iPhone 7 speaker when I have headphones plugged in

Hello,

1) Check the charging port for lint or other debris

2) See this: If your headphones don‘t work with your iPhone, iPad, or iPod touch

3): If no help, try this:

a) Open the Control Center

b) 3D press (or long press) on the music controls

c) Select the output option (little up-arrow with circles)

d) Select headphones

Good luck.