You are going to want to make sure your wireless carrier subscription is properly linked to your Apple ID first before you cancel any subscription. If there is any interruption in service, you will lose the playlists you have created and the downloaded music from the Apple Music service. How you do that will depend on your cell provider.
Connect Apple subscriptions from your wireless carrier or other provider to your Apple ID - Apple Support
Once you believe you have it linked correctly, it may even be worth a call to Apple Support before you pull the trigger to cancel the service through Apple. Express your concerns about losing data and they should be able to confirm the service being provided through your cell provider. It may not be necessary to perform this step, but there is no Undo button to make everything magically appear if something goes wrong.
Contact Apple for support and service - Apple Support