Doringkloof Centurion ADSL problems

[einameteish]

--Give a short explanation of the problem
Connectivity is up, but data comes through in short spurts with 3-4 second delays

--Give the first six digits of our phone number (like 011 425 xxxx)
012 667

--ADSL line speed (like 1Mbps, 4Mbps etc)
4Mbps

--ISP name and account type (like MWEB uncapped)
Afrihost

--The time of day when you typically see these problems
24/7

Optional, but it will be great if you can also give the following information:

--A traceroute to Telkom.co.za
traceroute to telkom.co.za (196.43.22.222), 30 hops max, 60 byte packets
1 router (10.11.0.2) 0.913 ms 1.450 ms 1.690 ms
2 105-236-4-129-esr-lo.mtnbusiness.co.za (105.236.4.129) 9.036 ms 10.850 ms 14.916 ms
3 ipc-recieve-rb-4a.za.mtnbusiness.net (41.181.178.89) 23.226 ms 25.677 ms 27.967 ms
4 rb-dca-2.za--rb-cr-1.za-a.mtnns.net (196.44.31.120) 30.806 ms 32.479 ms 34.448 ms
5 jh-cr-2.za--rb-cr-1.za-a.mtnns.net (196.44.31.95) 36.629 ms jh-cr-1.za--rb-cr-2.za.mtnns.net (196.44.0.42) 38.596 ms jh-cr-2.za--rb-cr-1.za-a.mtnns.net (196.44.31.95) 41.251 ms
6 qux-jh-dca-2.za-b.za.mtnbusiness.net (41.181.165.115) 47.324 ms 40.611 ms 40.626 ms
7 rrba-ip-se-2-wan.telkom-ipnet.co.za (196.25.58.17) 38.860 ms 41.700 ms 43.624 ms
8 196.43.25.137 (196.43.25.137) 48.924 ms 13.027 ms 16.023 ms
9 196.43.39.166 (196.43.39.166) 17.866 ms 20.061 ms 22.072 ms
10 rrba-ip-bssr-1-ge-2-48.telkom-ipnet.co.za (196.43.23.6) 25.707 ms 28.055 ms 29.804 ms
11 nbsc-ip-bssr-2-atm-5-0-0-1.telkom-ipnet.co.za (196.43.23.34) 33.219 ms 35.146 ms 37.359 ms
12 nbsc-ip-rcache-1-vif0.telkom-ipnet.co.za (196.43.22.222) 41.037 ms 43.801 ms 45.461 ms

--The actual sync speed of the line
512 / 4096 kbps

--The attenuation stats of the line
SNR Margin (Upstream) 13.0 db
SNR Margin (Downstream) 27.5 db
Line Attenuation (Upstream) 15.5 db
Line Attenuation (Downstream) 30.0 db