Bulge battery led to separation of front and back panel

While charging the battery, the front panel and the back panel separated from each other and a thin gap was created and immediately I switched the phone off and disconnected from the power supply. Subsequently the gap further widened and the battery, which had bulged, could be seen from the outside.

Escalated the matter through authorised Apple Service Centre and through Chat Service too.

Product: Apple iPhone SE, 2nd Generation (Black,128 GB)

The phone is less than two years old.