If you are trying to redeem your free Mp3s but it looks like you are going to be charged, be sure you are beyond the 7 day free trial period. Apple and Google Play will not let you skip the trial period. During the trial you can stream all 26,000 tracks on your mobile device.
When your 7 day trial has ended, your official subscription begins and your credit card will be charged. Now you can go to the website and redeem your free Mp3s.