3-month Apple Music trial not appearing on new iPhone

I’ve just bought a new apple iphone. I have never subscribed to Apple Music before. I want to access the 3 month free offer but it’s only offering me a month and I don’t understand why - I have followed the instructions to go to Apple Music and then if it doesn’t work to go to the Home button. Still no offer. My husband set up my new phone and he thought the 3 month offer went to my old phone initially although I have now reset that phone and given it to my son who had a different acct. He isn’t getting the 3 month offer so I don’t understand where it’s gone.