Fibre suppose to be fast and stable?

I have a 4Mbps uncapped fibre line from Telkom. After installation the router has given problems - this was going to be replaced, but never happened. I then bought a new router myself (Asus AC78U - pretty much top of the line). Still the connection is very unstable - especially in peak times. Forget about streaming video - I can't play online chess. In a blitz game (lasts 20 min) my connection drops twice (for a short while) - just to indicate how unstable it is. Technicians were suppose to call me - never did. Now I am being told they will likely charge a R1200 call-out fee.

Think I need to find another fibre and service provider - I have had nothing but poor service from Telkom in the last few years - simply cannot see my way open to continue like this.