How do I change the homepage on my browser using at&t
You don't mention what device or browser you are using, but I can tell you that it has nothing to do with carrier (AT&T). Generally, any mobile browser will have a setting for homepage. For example:
In the default Android browser: Within the app, press the menu button, and then Settings > Set homepage
For Chrome: https://support.google.com/chrome/answer/95314
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