How do I sync my old phone numbers to my iPhone?

MY iPHONE WON'T SYNC SONGS FROM THE LIBRARY ONTO PHONE? What do I do?

• For the first time ever, when I plugged in my iPhone, iTunes won't let me transfer songs from the library to my phone. I've transfered songs many of times but for some reason, it blocks it now. Also, when I try playin music from my iPhone it won't work. iTunes detects the phone and it appears on the left side but, I can play a song from the LIST on iTunes connected to my iPhone at the same time as a song from my actual iPhone (plays it from the speakers) Whats going on? Why hasn't it let me add more songs? Thank you for the help! :)

• Answer:

  Reset your phone. I haven't had that problem yet, but if I did, that's exactly what i'd do. If you have backed up your phone to your computer it will be okay