disappointed

A really disappointing experience at pepcell in blue route Tokai I bought a phone for my daughter for a 10year birthday after 4 day she complained about the battery being low even when charged at 100% . I took the phone back today.. they ask me leave the phone for a hour to be checked.. came back with my daughter they telling me they cant find anything wrong ...I explain and my daughter explained what was wrong with the phone after 4 day of using it..The manager told me she cant help I must call customers care ...to the disappointment of my daughter she show no care ....