Can I buy more GB for my iphone 6s plus

I dont have enough storage on my iPhone for the latest update. My problem is my music is taking up all my storage. My phone only came with 16GB which I thought would be enough. Ive deleted apps, got rid of any unwanted items that was using too much storage. Still unable to do the update all because my music takes up all the space. Can delete my music as its a family account. How do I get more GB's for my phone?