If i change mobile operartor and loose my "Premium" status temporaily and subsequently I enrol to Premium (not in a mobile bundle) will Ioose my offline tracks? What is the best way to proceed? Thanks in advance.
By "offline tracks" I am assuming you mean tracks that you set to download off spotify for use without internet, you will lose access to those offline temporarily, but can still listen to them with a internet connection.
Your playlists will not be deleted.
Vodafone will cancel your spotify, and your account will go to free, then when you purchase a subscription for the account yourself, you will just need to mark the songs to want downloaded to redownload.