Big big issue of No Service On iPhone is going to fix here, Continue watching for 1 min to till end your issue get resolved.
There are various reason for showing No Service On iPhone.
Check your payments with the plan. If not, then may be software errors.
Connect to Wi-Fi, Update Software of iPhone and look at Carrier Settings
To fix the cellular and Wi-Fi related problems of iPhone, anyone should reset network setting to factory setup.
Check Cellular Settings On Your iPhone. Sometime wrong setting effect the iPhone service.
Take a look at your SIM Card. Insert again in the sim card. If not worked check your SIM card in another iPhone.
Check for water damage. Apple will replace your iPhone (only when you have opted for an accidental warranty).