Except that before I signed up for fixed LTE, I confirmed with a CellC agent that I would in fact be able to use Fixed LTE in my area and it did work for about a month. I even have a printout of the conversation. So, nice try CellC, your fault, not the ISP's.
According to Afrihost, CellC has been using MTN towers in outlying areas but have since decided to no longer do so to save money, thereby knowingly cutting off a bunch of customers. Nothing to be done about it and no immediate plans to fix the problem.