Playing Offline Songs

[Proby20]

I have multiple playlists available offline on my iphone 5S, however I wanted to check whether when I play these songs whether Spotify will recognise that they are available offline and play them as such, or whether it will automatically choose to play them using 4G (and subsequently use my data allowance)? Do I need to turn off my 4G everytime I want to listen offline?

[Peter__]

Spotify should always play the local copy rather than streaming if available.