Unidentified/explainable object in the food and bad service from the manager

Just as we ordered at Nandos Southgate Mall, we experienced somewhat a terrible service with attitude from the manager after raising a complaint of something in the food that they couldn't identify.

My partner had just ate some of the things we ordered. The manager didn't even bother to ask what was happening but just gave us a refund and told us that we are getting a partial refund because we ate a potion of the food.

What mockery is this? she didn't even want to adhere or listen to anything that we wanted to say but is this the kind of service we get.

Forget the food but Nandos need to properly train their staff and teach them customer service especially if it is the manager.