It's always best to take a systematic approach to troubleshooting.
First, try to determine what sort of issue is it? Is the connection Intermittent, is throughput slow or is latency higher than it should.
Intermittent connections are generally either related to a line fault or router problem. To test your line, try connecting with a different ISP account (or a different router) and see if the problem persists. Also, for your router, disconnect all devices and switch the WiFi off and then connect a single device to connect. Then try connecting devices one by one and see if one of the devices causes the problem, or if it only occurs when WiFi is brought back up.
For problems that could be related to network, I highly recommend using our Network Test App. This will show you if there is any high latency on your line, and where the latency occurs. If the latency is on the first hop (to your router) it is probably a local network problem. If the latency is to the second hop, then it could be Telkom exchange congestion. If the latency occurs at the end of the traceroute, then it could be load on the server you are trying to access. Whever latency appears to suddenly spike is an indication of where the problem is.
Good luck :)