How to set up call forwarding on an iPhone through any major phone carrier

The method you use to set up forwarding depends upon the your cellular carrier.
GSM carriers like AT&T and T-Mobile let you set up forwarding in the Settings app.
CDMA carriers like Sprint and Verizon need you to dial a carrier code.
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If you plan to be in an area with poor cell phone coverage, or if you know that you won't be using your phone for a while, you can forward calls that would ordinarily ring on your iPhone to another number.

It's fairly easy to do and equally easy to undo when you want to restore your phone to normal. But the specific process depends on the kind of cell phone carrier you have, since there are two fundamentally different cell phone technologies in use in the US today.

How to forward calls on an iPhone with AT&T, T-Mobile, or other GSM carriers

AT&T and T-Mobile are the most popular examples of a kind of network technology called GSM. So-called mobile virtual network operators (MVNOs) like Cricket and Consumer Cellular use GSM as well, since, as "virtual" operators, they piggyback on a larger carrier in this case, AT&T's network. Similarly, Metro is a MVNO of T-Mobile, so it's a GSM carrier as well.

All you really need to know about GSM, though, is that you can forward your iPhone's number to another phone using the Settings app.

1. Open the Settings app.

2. Tap "Phone."

3. Tap "Call Forwarding."

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4. On the Call Forwarding page, turn the feature on by swiping the button to the right.

5. Tap "Forward To" and enter the phone number that you want to forward to.

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6. Tap the arrow to go back to the previous screen.

You're now set up to forward your incoming calls to the number you entered. When you're done forwarding, return to the Call Forwarding page and turn the feature off.

How to forward calls on an iPhone with Verizon, Sprint, and other CDMA carriers

Carriers like Sprint and Verizon use older CDMA technology for their network, and networks like Boost Mobile and Jitterbug are CDMA-based MVNOs of those larger carriers. If you have a phone on a CDMA carrier, you can't simply turn on forwarding in Settings like you can with a GSM phone. Even so, it's not very difficult; you just need to dial a carrier-specific carrier code in the Phone app.

To enable call forwarding, you obviously need to know the proper carrier code. If in doubt, you can find it on the carrier's website or by calling customer service. That said, the most common CDMA carriers Verizon, Sprint, and Boost Mobile all use the same code. To forward your calls:

1. Open the Phone app and tap the keypad button at the bottom of the screen.

2. Dial *72 followed by the 10-digit number you want to forward to. For example: *722125551212

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3. Tap the dial button.

Later, if you want to stop call forwarding, you need to enter another carrier code, and this one can vary by carrier as well. Here are the most common ones:

Sprint: *720
Verizon: *73
Boost Mobile: *720