Can you Activation lock iPhone 7 Plus?

You need the Apple ID and password that was used when the phone was first set up. If you don’t know that, you can’t remove the Activation Lock.

Since this is a used device, the previous owner needs to go to https://www.icloud.com/find/ and erase the device, then remove it from their account. If they won't do that, the device is useless. Apple won't unlock it.

Turn off Activation Lock - Apple Support.   *

Activation Lock is intended as a theft deterrent, and is intentionally not easy to bypass.

You don’t have the Apple ID and password associated with the Activation Lock, nor is the seller accessible, nor do you have proof of original purchase, which means you have no way to get the lock cleared or to get a refund from the seller and not enough proof of ownership for Apple to clear the lock, which means this iPhone is or is indistinguishable from a lost or stolen iPhone, which in aggregate means this iPhone is useless to you.

You got scammed. You’re not going to be able to use this device. Recycle it.

The All Too Common SAD Reality of Buying a used iPad/iPhone - Apple Community

If you need help with an Activation Lock after reading the Related Article above, please explain what help you need. If you need help with something else, more information would help.