While Apple cannot tell you the Apple Account email address, they do offer tips to help you find it.
If you forgot your Apple Account primary email address or phone number - Apple Support
If you are able to figure out the Apple Account email address, you can then reset the password.
If you forgot your Apple Account password - Apple Support
If you don't know the Apple Account email used, the only thing that can be done is to submit the original purchase receipt to have it removed from the phone. A third party receipt will likely not be accepted. That Apple Account is locked to the phone using Activation Lock and now you must prove that you are the owner.
https://al-support.apple.com/#/additional-support