Data sim card not working

MTN is by far the worst network. There is always something wrong with the network. I recently app**** for a router and data only sim 150gb (75GB anytime+75GB night time) i called the activations office and they activated the sim. On the 27th of March the sim card stopped working. I've been trying to get hold of them with no success. The 083 135 number, the automated voice just talks about a lot of UNISA stuff and at the end it says "goodbye". How does one even get hold of the call center agents? How do I keep paying for data that I am NOT using. MTN is just a big ****!