Q: Why dont i have garage band

Have a look at this support document:

Get Pages, Numbers, Keynote, iMovie, GarageBand, and iTunes U for free on your iPhone, iPad, and iPod touch - Apple Supp…

GarageBand is free, if you purchased the iPhone after September 1, 2014.

You need to sign into the AppStore  with your AppleID.

The first time you open one of these apps, sign in with your Apple ID. If you forgot your Apple ID, we can help you find it.

If you purchased a device with iOS 9 or later that's 16 GB or smaller, or if you updated your existing device to iOS 9 or later, you can download the apps for free. Follow these steps:

Open the App Store. Scroll down to Quick Links and tap Apps Made by Apple.

 

Tap the apps that you want to download. To download apps larger than 100 MB, your device needs to be connected to a Wi-Fi network.

Are you signed into the App Store with the same AppleID you used to originally set up your iPhone?

And are you in the same country?

Check, if GarageBand is in your Purchases history as described here:   Download your past purchases - Apple Support

If you cannot download GarageBand fro free, contact the App Store support.

use this webpage to get to the email form for the contact:   https://getsupport.apple.com