My Car's Oil Pressure Warning After Castrol Edge Oil Change

I took my car for maintenance, supplying parts from a reputable shop in Maslak auto industrial area to a private service. They changed the ignition coils, spark plugs, and performed an oil change using Castrol Edge Titanium 5-30w ll, a product I've used without issues for a long time.
After leaving the service, my car gave an "oil pressure" warning with an audible alert. I immediately pulled over and called the service, who advised me to return via tow truck.
Back at the service, no error codes were found during computer diagnostics. The mechanic suggested the oil might be counterfeit or have inappropriate viscosity. I objected, insisting I bought it from a reliable source. With no other apparent issues, they drained the oil, replaced the filter, and refilled with Mobil 2000 5-30w oil, all done in my presence without any other interventions.
A test drive showed no further warnings. I requested they keep the drained oil, saying I'd contact Castrol.
Today, I called Castrol and explained the situation. Despite offering my invoice and willingness to help identify the counterfeit seller, they said they'd only address the issue if I filed a lawsuit.
Castrol seems unconcerned about potential damage to their reputation or identifying counterfeit sellers. For a ₺1600 issue, they're asking me to go through the Consumer Arbitration Committee and then file a lawsuit.
I condemn Castrol for not standing behind their product or supporting their customer. I'll never buy their products again and will share my experience to inform others about their company policy.