I want to unlock the Apple XR activation lock I have a purchase invoice

Hello ~ Did you buy that iPhone used and it was activation locked? If so return it for a refund. Take a look here:

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

Also:

The All Too Common SAD Reality of Buying a Used iPad/iPhone

~Katana-San~

I can tell you right now that Apple is not going to remove the activation lock.

You need the original proof of purchase from an authorized retailer.

That's not what you have. You bought a used phone. Return it for a refund. it's unusable. There is no way to bypass the activation lock.

How to remove Activation Lock - Apple Support