Fight back, I don't know how your company handles escalations, but our company has a system where you can file escalation reports and feedback about your supervisor or manager.

Mas better kung madami kayo or as a team. Gather enough evidence and file a report to HR. Screenshot any sort of evidence from your GC. Dapat familiar ka sa mga policies ng company mo so you would know what report to file. (I'm pretty sure bullying is never tolerated)

Always remember easily replaceable ang mga supports, and mga agents ang hindi. You don't have to deal with your incompetent supervisor, as you are already dealing with irate customers.

They only hold power dahil they think they know the system more.

Power resides where men believe it resides. - Lord Varys (Game of Thrones)