How come on my iPhone 5S, when I try to play music on the Spotify App, it doesn't work?

Every time I click a song, it tells me that I have to be a Premium account, but when I play Spotify on my laptop, it works. How come I can't play any songs on my iPhone on Spotify?

That message states that you must have a Premium Account, and not the TRIAL version…

Are you sure that you paid for the Premium Account?

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