My S3 is running like crap and I am trying to track down a used S4 to hold me over until the highly rumored Galaxy S5 Prime comes out. Anyway, can I just buy the S4, swap the SIM from my S3 and the S4 will work fine? Will Verizon charge anything since I switched my phone? Is there only a fee if you sign up for a new contract and get a new phone?