This is not the most recommended way, but try to short the + & - in the PHONE only, the way to kick back some battery's in my experience (and i do have some hehe) is to apply MAX 4.2V to the battery directly + to + & - to -. this is directly to the circuit (plastic top).

Shorting the phone + & - could remove any power stored in capacitors, this would be the same that happened after some days of just laying around.