Hi. If you've changed your phone but swapped your old sd card in then it will contain the cache from the previous Spotify install. Unfortunately this cache is encrypted and the key to decrypt lies with the Spotify app on your old phone.
You'll need to do a clean install (follow the guide linked in my signature) and redownload any Playlists or albums you want to be able to listen to offline.
Please use the search feature before posting a problem/bug/idea. What's a Spotify Rock Star, and how do I become one? Using Spotify Since March 10th 2009 Twitter: @mechanimal82