My wife's Rezound hasn't had 4G for weeks. She got another SIM card two times and it didn't make a difference. She's been on 3G. This afternoon her extended battery was low and she popped in the stock one. Lo and behold she got 4G and it stuck. I have the same extended battery in my Rezound and this hasn't happened to me. We got them from Verizon Wireless. Why would this happen? Are the batteries under warranty? I wonder if they (Verizon) will help. Thanks.