I bought a used iphone and the previous owner forgot to delete their icloud account, so I cant add mine. Is there anything I can do?

You are experiencing Activation Lock. If the previous owner will not remove the device from their account there is nothing you can do unless the place you purchased it from will give you a refund.

iCloud: Find My iPhone Activation Lock in iOS 7

What if I purchase a device that is still linked to the previous owner's account?

Contact the previous owner as soon as possible and ask them to erase the device and remove it from their account. For complete instructions, read how to remove a device from a previous owner's account.

How do I check for Activation Lock before purchasing a used device?

When purchasing an iPhone, iPad, or iPod touch from someone other than Apple or an authorized Apple reseller, it is up to you to ensure that the device has been erased and is no longer linked to the previous owner’s account.

Follow each of these steps to make sure that you can use the device you purchase:

icloud.com/find

. Do not take ownership of any used iPhone, iPad, or iPod touch until it has been removed from the previous owner’s account.

You will know that a device is ready for you to use when you are asked to “Set up your iPhone", “Set up your iPad", or “Set up your iPod” during the device setup process.

There is nothing you can do to defeat orbypass the Activation Lock. The previous owner must unlock it for you. If you can not get your money back, turn the iPhone in to the police as it is probably stolen property.