Reconnecting my account from outside the US

Hi there! 

I had a prepaid plan or Gophone plan while I lived in the US, until late June 2014, but now my account has been disconnected. Soon I will be traveling to the US and I want to reconnect the line and add balance so that I can use it  while I am there (for calls, texting and data.)

Also, I need to know if I will be keeping the same phone number, as I read that I could lose my number. How can I find out this? 

Finally , I wanted to know if I can call a toll-free customer care number outside the US from a line number. 

Thanks!