Also take into account the other costs such as termination fees; often a $99 termination within 6months, and contract termination fees. Some providers also offer a 12/24 month contract with free modem. Although if you bought the modem outright, contract is not needed. same goes with the setup fee or transfer fee.
If you decide to cancel the contract down the track some providers may make you pay out the remaining months in the contract; others will offer a small termination contract fee ~$99 or something.
I work for an ISP in Perth; and often had to check the other providers pricing and plans when dealing with customers when working in support.
Also check what costs are involved if you want to upgrade the speed of your connection; or change your download quota plan. Speed upgrade costs isnt a factor with ADSL2+ only ADSL; as you have 256/64, 512/128, 512/512, 1.5/256 with ADSL standard. same goes with downgrading.
Dont be afraid also to ask if they will better a plan offered by another ISP.
They may however commit to the offer on conditions; such as a termed contract.
And lastly. If they do offer a discount or matched plan, conditions etc, ensure you get it in writing and confirmed with employees name; etc before signing and submitting your application.
This will save you difficulties down the track if they try to get smart with terms and conditions.
Hope this may help you and others considering broadband also; whether new users or existing.
