Here are some of the most common iPhone 7 issues and their respective fixes such as No Headphone Jack, Toggling Airplane Mode Causes No Service or Cellular Coverage, Poor Battery Performance and Sluggish Overall Performance.
No Headphone Jack
Getting an Apple Lightning Dock.
Toggling Airplane Mode Causes No Service or Cellular Coverage
When the Airplane mode is activated and deactivated afterwards, iPhone 7 / 7s is stuck with not being able to get any reception or signal. Try to turn the Airplane Mode on and off a couple of times until the phone acts normally. Restarting the phone altogether may also help on certain occasions.
Poor Battery Performance
Looking at Battery Usage in Settings will shed some light. If all is normal and the battery still keeps dying rapidly, asking for a replacement might be in order.
Sluggish Overall Performance
If, at some point, that the phone starts acting weird, the most common solution is by restarting the phone. Most of these problems go away after restart, but if this fails, factory reset might help. If factory reset does not fix all these, requesting for a replacement will be the best option in order to get the iPhone 7 running normally.