How do I get a new charger for my 7-month-old iPhone?

Set up an appointment at an Apple Store or Authorized Service provider so they can check it out and replace it under warranty if required. Accessories like the cable and included charger are covered by the iPhone's warranty.

click here ➜ Apple Service and Repair for iPhone - Apple Support

Go to this page to find your nearest Apple Authorized Service Provider (AASP) or Apple Authorized Distributor (AAD) --> https://locate.apple.com/country

How to make a Genius Bar appointment

1. Go to https://www.apple.com/retail/geniusbar/

2. Go to "Get hardware help".

3. Select your hardware and continue selecting options requiring replacing parts until you see "Bring in for Repair"

4. Sign in with your Apple Account

or:

Refer to this document for ways to contact Apple ➞ https://support.apple.com/choose-country-region

Select your country (also look for "other" regions), then a product. If you don't see one that handles your issue then keep experimenting with selections until you reach one that gets you a chat session or a telephone call and get the representative to redirect you.

or:

Contact Apple for support and service by telephone ➞ https://support.apple.com/HT201232

The replacement may be covered by warranty.

apple no longer ship ac chargers with their iphones

so the ac charger would have it's seperate warrenty not related to the phone

Legal - Hardware Warranties - Apple

apple do not set the warrenty rules, those are set by the government in your country

Warranty - Wikipedia

so unless apple can prove that the ac charger is defect because of user handling they should validate their warrenty and replace it at not cost to you.