Seems like its ur first encounter for such incident.

Next time call ur own insurance company first to inform. If can drive, the  go lodge  police report first. If cannot drive, call insurance to tow the car back to Proton Paint & Body Repair workshop. Proton officer will assist and help u from there for all the claims and repairs.

For ur current case, u probably voided all ur warranty from Proton as the third party workshop might not be using original parts to repair. Its common workshop practice to claim original from insurance company, but provide used or non-genuine OEM parts in order to maximize their profits margin.

Try ask if the repair can change to Proton Paint & Body for claim or not. Big chance they say cannot la, but u can alwis reconfirm with ur insurance company.

Why not sending it to body and paint centre? Claim his insurance