To access Apple's music streaming service in iOS 8.4 you must sign up for the 3 month free trial, but you do not need to worry about being charged once it expires if you disable the automatic renewal. Here's how:
1. Open the Settings app on your iPad or iPhone.
2. Tap iTunes & App Store.
3. Tap your Apple ID or sign in to your account.
4. Tap View Apple ID on the pop up box.
5. Scroll down to "Subscriptions" then tap "Manage".
6. Tap the the Automatic Renewal slider so it is OFF.
You will now be able to access Apple Music for free without being charged $9.99 in 3 months when your trial expires.