Activating a Phone on AT&T: New Lines, Upgrades & Ports

Activating a new or upgraded phone on AT&T is an essential step whether you’re starting a new line, upgrading an existing device, or porting your number from another carrier. Many people think transferring their content or setting up their eSIM automatically activates service, but that’s incorrect—these steps only move your data and number, not your active cellular service.

What Really Activates Your AT&T Phone?

To officially activate any new line, upgraded phone, or ported number, use one of these approved AT&T methods:

• Go to att.com/activations/activatewireless and follow the guided process.
• Call the automated AT&T activation number: 866-895-1099.

These will link your device’s IMEI and SIM/eSIM to your account, activating service on the correct line.

Content Transfer vs. Activation

It’s easy to confuse content transfers (moving your photos, contacts, apps) or eSIM transfers with actual activation. While both processes are important when setting up a phone, neither triggers carrier activation—the phone won’t have active cellular service until you complete activation via the official AT&T activation page or automated number.

What About Number Porting?

If you’re bringing a number from another carrier (port), do not cancel your old service before the port. AT&T handles the switch for you to avoid service gaps. When the port is ready, activate your new device using the AT&T activation tools listed above.

Text messages may take a day or two to fully route after porting—reset your network settings if needed, or contact AT&T customer support.

Upgrade & eSIM Swaps

For upgraded lines or swapping eSIM profiles, always finish the official AT&T activation (online or by phone) first. After that, you can transfer your content or move your eSIM if eligible, but only an actual activation makes your device ready for use on AT&T’s network.

Quick Step-By-Step

1. Insert your new SIM (or set up eSIM, if directed).
2. Visit att.com/activations/activatewireless or call 866-895-1099.
3. Follow prompts to enter your device details and complete activation for your new line, upgrade, or port.
4. Once active, transfer your content (see: Smartphone Content Transfer) and eSIM as needed.
5. If you have trouble, contact AT&T customer support to ensure your phone works as intended.