This device is linked to another Apple ID account
So I bought a phone from a person and I reset everything new. Set it up as a new iPhone and signed in with my own iCloud. Then when I went on music to pay for the music services it said "this is device is linked to another Apple ID account" and it had what other people said "can't transfer again after 90 days if I transfer now"? It had a "transfer" button and a "cancel". I hit cancel for now and went on my Apple Music to check if its my account its signed into and it sure is. Is someone's account still linked to this iPhone even though i reset it completely. Why? and how do I remove it. I don't want some other account linked to my phone. That's the whole reason I reset it.
iPhone 7 Plus