Thank you so much for your reply.
I understood that if I refill $100 on 2/28 2014 Account expiration date will be 2/28 2015 and cancel date when I loose my phone number will be 4/28 2015.
01. Is this correct?
02. Does my one month for $50 plan start on 2/28 2014 automatically and end on 4/28 2014?
03. I live out of the US and I do not use this plan from 2/28 to 4/28 2014. If my next trip to the US is 9/1 2014 for two weeks and another next trip is 2/1 2015 for two weeks, is there good way to use $100 just for both trip of 9/1 2014 and 2/1 2015 not loosing my phone number?