help with adsl connection

hey every1, i am new to this forum and would like some help getting my adsl connection working properly. here's my story.

i was originally with AAPT adsl on 1500k which worked fine. unfortunately the 15gb download limit (before getting choked to 64k) wasn't enough download for myself and flatmate combined. so i switched to Koala Telecom at 1500k again. the first day it seemed to work fine then i started to have problems. my pages just wouldn't fully load. i was able to log into my modem (via 10.1.1.1) at this stage. but now after reinstalling the modem drivers it seems i cannot log in anymore. i was hopping to figure out how to make the network secure so that only myself and flatmate can use it. i have also tried 10.1.1.2 (for usb cable). is there any programs i can get that will monitor adsl connection problems? i can't figure out if it's something i need to do or if it's koala telecom that need to fix the problem. i'm not really a wiz at this sort of stuff so if someone could help me that would be great.