I found an AT&T SIM card in my new iPhone. Does that mean it's used?

If you bought the phone directly from Apple and ordered AT&T service with it the phone might come with an AT&T SIM. There is no other reason there should be an AT&T SIM in any “new” iPhone. Where did you buy the phone? If it wasn’t an Apple store or apple.com, or an Apple Authorized reseller, you might have bought a gray market phone purchased in the US, then shipped elsewhere to be resold. You can check for this by entering the serial number in this site→Apple - Support - Check Your Service and Support Coverage

The warranty expiration date will by 1 year from the date the phone was originally sold.

You bought a gray market phone that was illegally imported and resold in Dubai.

It is not “new”. Technically, it is used. It may also be locked to AT&T.

The warranty, if it is still valid at all, is only good in the US.

KiltedTim wrote:

It is, by definition, “not new”. It was sold by Apple or an authorized retailer, then re-sold, possibly multiple times, before you bought it.

But probably not if the warranty check shows one year remaining.

It is, by definition, “not new”. It was sold by Apple or an authorized retailer, then re-sold, possibly multiple times, before you bought it.

It is a new phone. It should not have an AT&T SIM, however, unless it was financed through AT&T.

What happens when you put your own SIM into this phone? Does it work or do you get a "SIM Not Valid" pop-up? If you get "SIM Not Valid," your phone is SIM-locked to AT&T and can only be unlocked by AT&T. If the phone works with your own SIM, enjoy your new phone. Good luck.

What is the model number? (It ends in /A)

vaishakh18 wrote:

Hi it’s working as normal

Great! One last thing to check: Go to Settings/General/About and see what it says for Carrier Lock. If it says “No SIM restrictions” you’re good to go.

Where, exactly, did you buy the phone?

You should be able to get warranty service anywhere in the world, subject to some technical limitations. I know this through personal experience.

In general, any physical defect that does not require marrying a replacement part with the device's CPU can be addressed anywhere in the world. This includes things like screen replacements, battery replacements and back camera replacements. Troubles related to security features, like Home button failure, cannot be "repaired" outside the country of first sale.

When my month old US iPad's Home button stopped working in Japan, Apple Japan told me that they couldn't obtain the parts to fix it (a Home button that could be married to my US CPU), so they replaced my new US iPad with a new Japanese iPad. No muss, no fuss. When my Hong Kong iPhone needed a new battery during the battery scandal a few years ago, Apple Singapore happily replaced the battery for the discounted price.

Some things that cannot be attended to outside the country of first sale include warranty exchange of a bad phone from a highly restrictive country (like one where FaceTime is illegal) in a country where such restrictions don't exist.

Since you have a US phone with no SIM lock and a full year warranty showing on the screen, you should relax and enjoy your new phone.

Shichimi wrote:

You should be able to get warranty service anywhere in the world, subject to some technical limitations. I know this through personal experience.

Apple reserves the right to limit warranty services on an iPhone to the country or region of original sale.

IMPORTANT RESTRICTION FOR iPHONE, iPAD, APPLE TV and HOMEPOD SERVICE.

Apple may restrict warranty service for iPhone, iPad, Apple TV and HomePod to the country where Apple or its Authorized Distributors originally sold the device.

Legal - iOS Warranty Document Us - Apple

You may have gotten lucky but there have also been lots of people posting here who have been less lucky.