The ratings API offers two type of rate, "commercial rate" and "counter" rate. Commercial rate is the discounted rate you received based on your volume or agreement (contract number must be included in your request), the rate you will be charged through EST online. The counter rate is the retail rate, which is the over-the-counter rate you will receive when shipping from the post office. Please make sure you are requesting the correct rate type.
To change this to commercial. for your reference here is where you can find this option
System > Configuration > Shipping Methods > Canada post V2. Scroll down to where you see Quote Rate. that can be changed to Counter or Commercial.