HELP, my blackberry won’t come ON

Hello TR community,
Please help me, my blackberry won’t come on, when my blackberry attempts to reboot,it comes up with the (X no battery signal) while connected to the charger.after charging the battery full with a universal charger,it doesn’t still come up after inserting the battery.even after replacing the battery with another one,it still refuses to come up.I don’t know if its an operating system error. The model of my blackberry is torch 9800. Please HELP…..