How can I get into the iPhone I just bought with out a passcode

That does not change the fact that the phone is locked. And it is probably locked with Activation Lock which cannot be defeated without the correct Apple ID and Password. Since it wasn't prepared properly for a new user, I suspect that it is a stolen phone.

Casper0821 wrote:

How can I get through the original owner s passcode

If this used device still has a passcode, chances are extremely high you will go on to encounter Activation Lock even if you remove the passcode.

It would seem the seller did not properly prepare this device for resale.

If you can return this for a refund, you should.

You need access to a computer. You could potentially go into an Apple Store if one is open near you and they might let you do it there but the main problem is it might not work. If the product is Activation Locked you will not be able to get into the device.

If I was you, I would return the product to where I bought it from as it is highly unlikely the above step will work meaning the phone to you is useless. If you are unable to return it, you might want to look at recycling options.

That's irrelevant and has nothing to do with the passcode. If there is a passcode on a second hand device that you just purchased, you will need to have the previous owner either tell you what it is, or properly erase and format the device for you. If the seller is unwilling to do either, then you should demand a refund and return the product if possible.

Follow the instructions here: If you forgot the passcode for your iPhone, iPad, or iPod touch, or your device is disabled

You could restore iOS to remove the passcode, but if it's activation locked, you'll be left with a brick.

Casper0821 wrote:

I've got at&t service I put my SIM card in and it shows at&t LTE in top left of the phone

Are you still being asked for a passcode you don't know?