\Not registered on network"message from Cell C"""

My Galaxy S4 has been completely offline for more than 2 days. I am not able to recieve or make voice calls, I cannot send, nor recieve messages, and I have absolutely no data connectivity. This is infuriating, since the sim card is on contract, and I am paying upwards of R600 pm for absolutely nothing in return. My phone displays a message saying \not registered on network"/ \""Network (RSA CELL C) is unavailable\"". despite having tried ENDLESS times to register on the network manually"