Poor payment system

I worked as an Exam Assistant in July 2018 and to this date I haven't received my salary as yet. The funny thing is that half of the people I worked with during that time got paid and the rest of us are still waiting for the money that we worked hard for. Apparently they have a new way of making payment due to people who worked there and my question was why did not all get paid at the same time with the other that got their money and there was no valid explanation for that. 3 months full now going on 4 since I worked there and I still haven't recived my money.