l can't afford air time its been two months l haven't called anyone because I'm broke

In this post I will round-up a collective list of Cell C USSD codes (Unstructured Supplementary Service Data). It may not be a complete list and / or the only guide as this post title suggests, but I do want to believe I have listed most if not all the important Cell C USSD codes.
But, with YOUR help, we can make this list complete. So if there is any USSD command I have left out, please mention it on the comments section below.
I have also tried to give steps (where necessary) on how to complete an intended USSD queries. I have also included links to broader posts which have thorough information on a particular subject.
Disclaimer: All Cell C USSD codes mentioned on this post were correct at time of writing this post and Cell C can make changes at anytime.
With that said, I would appreciate a heads up if anything on this list does change.