Looking at that 5.x SNR, means 1 of 2 things, your router is faulty or the copper line is faulty.
If telkom tech tells you the line is fine with a SNR of 5.x then they are lying str8 in your face and pulling the wool over your eyes if you believe them.
Let them sync your line at 2 or 4mb to get it more stable.
And the advice from the Afrihost tech is spot on, something is wrong because with the SNR you going to get up and downs.
Generally a value below 6dB is of concern. Sometimes that's the best it can stabilise at and I've occasionally seen some clients manage a workable connection on 5.5dB. Remember a dB is a ratio, not an absolute value, so it's really just a guideline. We generally like to see at least 12dB for a healthy connection.