I can’t seem to get my three months free. It just says 7 days free trial.

Hello and welcome to the Apple Support Community Forum!

In order to claim the 3-month free trial you must meet the following criteria:

• Must be a new phone or sold as used within the first 90 days of ownership (Assuming the previous owner of the device didn't claim it themselves)
• The trial must be claimed within 90 days of the purchase of the iPhone otherwise the offer will expire.

If you meet the criteria and still can't get the offer; I would contact Apple Support directly (Official Apple Support).

Hope this helps!

Read here about the conditions for the offer: Apple TV+ offer - Terms and conditions - Apple