Songs stopping after 1 1/2 songs - not streaming properly

[yanushs21]

I have Spotify premium and when I go to any of my playlists and play a song, it only plays for about 4-5 minutes and then it abruptly STOPS, not pauses, but fully stops and I need to go back into my playlist and either select the song to play from the top or select a different song. I only use offline mode when I am using my phone to avoid data usage so I don't know if this happens when I'm not in offline mode but I am pretty sure it does. 

I am using a Samsung Galaxy S5.

I purchased Spotify premium solely to be able to use offline mode on my mobile whilst in my car or elsewhere without any ad interruptions, but I'm not sure what's worse, ad interruptions or having the stream stop playing altogether! I've had Premium for about 6 weeks now and have been waiting for a bug fix to be released but nothing has happened yet and the problem persists. I have tried doing NUMEROUS clean reinstallations and have even reset my entire phone but nothing seems to work. I don't think it's fair for me to be paying for a service that doesn't work properly... can anyone help?!