iTunes purchase button not responding on iPhone

I’m trying to buy a ringtone on iTunes on my Apple phone and when I go to purchase it, the double click button or the cursor slide button doesn’t work. I tap on it or try to get it to move and nothing happens. What do I do?

[Re-Titled by Moderator]

Original Title: I can't purchase a song on iTunes because when I double click or slide the cursor, it doesn't work