Complain with the Service in McDonald's Krugersdorp

Now as I'm at restaurant in McDonald's Krugersdorp, we ordered food me n my sister for a sit in and at the same time I wanted to enquire about doing my son his first birthday here on the 16th November so I was told by the cashier that the is no one to assist me as they from a different restaurant in Florida, I then requested to speak with the manager, his name tag is not on his shirt but the cashier said he is Sikhombozo n shouted out loud that he can't help us.

So I would like to know what I should do with this situation as it's my family favorite restaurant and the closest from Randfontien.