Really unstable connection

I had my new fibre line installed by Open Serve two weeks ago. I have yet to have a solid stable internet connection! It drops for 10/30 seconds every hour or so and despite having the installation guy come back and resplice the cable and check everything it is still dropping. Now the installation guy refuses to help and says speak to Telkom who have no idea how to fix my wifi and make it stable! it is affecting my work really badly! Avoid Open Serve