How to get inside a HTC Double Charge power bank?

I have an old HTC Double Charge power bank with a (supposedly) dead battery. I decided to refurbish it, but don’t seem to have an idea on how to get inside.

As far as i can see there are no screws, pressing the case here and there doesn’t show any sign of “clicking” fasteners, and tools used to take other cases apart don’t seem to help, either. Has anyone successfully disassemble such a device before, or at least have any ideas how to get inside?