Second hand apple watch

I had a Apple Watch Series 3 bought for my birthday yesterday, whilst setting it up it says on my phone that the watch needs a software update, so I pressed continue and it comes up needing Apple ID password and email address, I enter mine and it says it’s not my password and email it needs, it’s the previous owners Apple ID password and email, it comes up on my phone that they have got to disconnect there Apple ID from there end, which they say they have, and it just won’t unlock, I can’t even get any settings up on the watch either.