I have 3 unlimited data iphone 4S and 1 2GB iphone 4S. My data usage for all phones is about 6GB per month (these are all verizon phones). I also have an ATT ipad 3 that costs me 30.00/month for 2GB and unless I am traveling i never go over. If I went to the share plan, I would not get killed but i fear that the 4G/LTE phone will be faster and allow for much more data usage overall. If i purchased a new iphone from Craigslist would I be albe to keep my old unimited plan?