Ringing can be caused by a voltage spike on the copper pair, which is not always due to someone actually calling your phone number but may be due to other interference
First ask yourself: Do you really need a working land line? I thought I did until our Telkom lines got stolen and I was forced to use a mobile phone for a few months. Well, I got used to having no landline, and since it got repaired months ago, we haven't used it once. So I would suggest trying to break your dependence on a copper voice line and to rather switch to mobile calls where possible, even if you use Skype or WhatsApp calling.
but let's assume that you actually want to continue to use that phone line for voice phone calls and need to ensure that a phone can ring on that line:
The key to know the cause of the ringing is to pick up the phone when it rings:
- If you just hear a dial-tone, then it is probably interference causing the ringing, and the best suggestion is probably to call Telkom out to check the voltage levels on your line. They'd then need to make sure that there is proper earthing on the DP, that there is no other crosstalk or interference between your line and another customer/s, and and that the correct filters are in place.
- If you don't hear a dial-tone, but instead it seems like there is a call in progress but the other side does not talk back to you, then you could try something like Telkom's IdentiCall to try find out who is calling, or if that fails then report the issue to them so that they can investigate the matter for you further