My own iPhone 7 is locked with foreign account after simple reset I have an issue with my iPhone 7 Plus, which today I wanted to replace with the XS.

After backing it up to a Macbook and then resetting the old phone, I logged in to the Apple ID site to remove the IPhone from my account. However, it wasn't there!
All of this took maybe 20 minutes.

Now I can neither restore the backup from the Macbook through iTunes, nor can I set up the old Iphone as a "new Iphone" anymore. Both attempts lead to a screen saying that the Iphone is locked to an account "n*****@icloud.com", which is not me! My account is "a**********@p*******.de"!

The SIM card is not locked in any way, I bought the phone without a cellular plan! The restore doesn't work with or without the SIM card.

I bought this iPhone brand new from a trusted retailer, and the iPhone has always ever only known my own Apple ID!

I cannot reset the iPhone through ITunes, or any other way.

How can this happen and what do I do? I fear I have to go to an Apple store and explain the dilemma. I do have the original receipts and can prove this is my phone that way, hopefully!
If you have all the original receipts required to prove ownership please go to the next Apple Store (or contact Apple support if there isn‘t a store close by). They should be able to reassign the phone. 

PS: Make sure you make a fresh backup after your old phone is unlocked. Don‘t think there is a way to „unlock“ the existing backup.