purchased a pre-owned device now its showing iphone locked to owner

As is, unless you can independently obtain assistance from the previous owner, the iPhone is (and will remain) useless to you. If you are able to contact the original owner, they will require this information:

What to do before you sell, give away, or trade in your iPhone or iPad - Apple Support

Here are the Apple support pages that outline the Activation Lock - and the only mechanisms by which it can be satisfied:

Activation Lock for iPhone, iPad, and iPod touch - Apple Support

Turn off Activation Lock – Apple Support

As you will discover, unless you are the owner of the AppleID that was last used to activate the device, you’ll not be able to defeat or bypass the Activation Lock. With documentary evidence that you are the original owner (such as the original sales receipt showing the serial number), Apple may be prepared to assist - otherwise they and nobody here will be able to help you.

The All Too Common SAD Reality of Buying … - Apple Community

Here is what Apple suggests when purchasing a previously used device:

Check for Activation Lock before you buy a device from someone else

Before you buy an iPhone, iPad, or iPod touch, from someone other than Apple or an authorized Apple reseller, make sure that the device is erased and no longer linked to the previous owner’s account. Follow these steps to check if the device is ready to use: 

1. Turn on and unlock the device. 
2. If the passcode lock screen or the Home screen appears, the device hasn't been erased. Ask the seller to completely erase the device by going to Settings > General > Reset > Erase All Content and Settings. Don't take ownership of any used iPhone, iPad, or iPod touch until it's been erased.
3. Begin the device setup process.
4. If you're asked for the previous owner’s Apple ID and password, the device is still linked to their account. Hand the device back to the seller and ask them to enter their password. If the previous owner isn't present, contact them as soon as possible and ask them to use a browser to remove the device from their account. Don't 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're asked to "Set up your iPhone," “Set up your iPad," or “Set up your iPod” the first time you turn it on.

If you see a "Locked To Owner" message, one referring to iCloud locked, or activation locked:

Take it back to the person from whom you received it. Get them to do the things in this support article or ask for a refund --> What to do before you sell, give away, or trade in your iPhone or iPad - Apple Support There is no way of discovering the owner of a device unless they left a message to display on the device when it is turned on. For information about how to request access to a deceased family member's Apple account data, and possibly their equipment, read this support article --> How to request access to a deceased family member's Apple account - Apple Support

Unless you have the account information that set the lock, the original receipt from Apple, or can demonstrate legal inheritance from a deceased owner, you cannot remove the lock; recycle the device. Read this article about how to remove Activation Lock --> How to remove Activation Lock - Apple Support

From the very bottom of Apple Trade In - Apple :

"Does Apple offer recycling?

Yes. Apple Trade In lets you recycle any Apple device (including devices from Apple-owned brands) at any Apple Store and on Apple for free. That includes your batteries and old electronic products as well as free, on-demand packaging recycling for our commercial, education, and institutional customers. When we receive your device, it will be thoroughly inspected to determine if components can be recycled or reused. Whether recycled or reused, all activities relating to the processing of your device will be managed in an environmentally responsible way."