If your iphone is still under any warranty, best go back to apple tech support. It might initially be a bad battery pack. Does this happen when it is plugged into iTune on PC or Mac computer? Update: Have you tried backup everything and do a factory reset on iphone? a clean reboot with empty data and maybe even before activation then try to charge with original apple charger and computer to see if works. If can show charging try to see if charged 100% before further use of iphone. It seem to me some kind of software problem since u have changed to new one n still cannot charge. Assuming the batt pack is apple original...

(1) Press the "Home" a few times to try get it out of freeze mode; (2) Still freeze? Long press the power button till it prompt for restart or restart by itself.