try a soft reset, while ur phone is on ( if u can put it on at all) take the battery out of it wait for 30 secs - 1min and put it back and turn on and plug the charger, it should either be on if any charging is left or will show the charging icon. If still doesn't, it needs a battery change, call up the customer care.
I work in BB Specialist team at Orange, its a specialist advice take from me