Has there been a lot of rain in your area in recently months? If so, that would provide a potential explanation as to why you went for a few months with no disconnects, and then all of a sudden they started again (i.e. rain got in, or underground water level rose, and this interfered with your line and perhaps started some corrosion on it).
Get a Telkom technician to come out. Go with him to the local exchange where your line connects through. Tell him to plug his little machine in. Make him show you the readings on the "A channel" and the "B channel". You want these readings to be LOW. If they are high, that means there is dirt and water and other things interfering with the part of your line between the exchange and your house. If the readings are high, instruct him to 'find clean channels' for both wires.