I want to get the iphone 3gs using the add a new line feature. I am currently not using an iphone (sold it). I want to add a new line to get the subsidized pricing on the 16gb iphone 3gs ($200). I then want to cancel the old line, paying the pro rated ETF. Lets say I get the iphone 3gs on the 19th, do I have to wait 30 days before i cancel the old line? My minutes currently reset on the 17th of every month.