The authorized 4S center knew can't cover the repair billing just by claiming the 3rd party insurance. Hence sub it to "bengkel bawah pokok".

In future, if one wants a smoother transaction.
1) Send it to an insurance panel & close one eye.

If u insist u want a perfect repair, hire ur own lawyer, ur lawyer would then hire an adjuster. Paid for the repair thru ur own pocket 1st. Then ur lawyer would claim from the other party's insurance. The final compensation amount may be enough or may not be enough to cover ur cost.

Ur lawyer would list the repair cost, adjuster report cost, lost of use compensation, and whatever items to jack up the amount. While the opposing insurance company would counter offer a settlement amount, which usually ur lawyer would just accept.