I just purchased this modem to replace an old TP Link W8690N 2 weeks ago. When I used the Asus modem at that time, the connection speed was fine, but connection kept dropping. I called Spark and they fixed it last week (they said there was a wiring problem on the street side).

After they 'fixed' the wiring, the new modem had slow speeds. With the old modem, the ADSL speeds are normal (around 10 Mbps download and 0.9 Mbps upload), but on the Asus modem, the speeds drop to 0.2 Mbps down. The modem reports DSL down link speed of 7769 Kbps. I have set up the modem according to Spark's settings on their website.  I thought the modem broke at first, but I have tried it at my friend's house (they also have ADSL and use Spark and also live in Auckland) and it works completely fine and has good speed with the default settings. I also tried different phone jack wires, splitter (we have landline) and another telephone jackpoint, but it has the same problem. I connected my old modem's Ethernet output to the new modem's Ethernet input, with that the speed is acceptable. 

Screenshots of the settings page: 

The line attenuation is about 14.5 dB, the SNR margin is around 7.8 dB. From what I understand, the line attenuation is normal but I don't know about SNR margin.

I have already had Spark technicians come to my house again to check wiring, but they said they won't help us at all with non-Spark modems. They said the wiring is fine, after they fixed it last week. Any ideas how to fix the problem?