Unable to install AT&T to iphone

Please I need response as soon as possible 

Install what? The AT&T app? Your post doesn't make a lot of sense.

Hi @Eddrich_

We understand that you're unable to use AT&T app, and we here to help you.

Please refer to the below steps to log in to my AT&T app.

Restart your device if the app isn't responding:

1. Restart your device, then open the myAT&T app.
2. Sign in with your user ID and password. Be sure to delete any IDs you’ve saved first..

Reinstall the app if restarting doesn’t help:

1. Delete the myAT&T app from your smartphone or tablet.
2. Download the latest myAT&T app:
   • Go to att.com/myattapp on your smartphone or tablet.
   • Or text myATT to 556699 from your wireless device. We'll send you a link, so you can download the app.
3. Install the app, then open it and sign in.

Check your device operating system (OS):
Make sure you’re using the latest app version on your device. To learn more about your OS, go to Device Support. We supported these OS versions:

• iOS 12.1 or later

Here's the link which helps you using AT&T app: https://www.att.com/support/article/wireless/KM1048751