Just a note on 3HK's current pricing. You are better off going on the $148 for 200MB plan, rather than the $198 for 300MB plan, even if you are going to use 300MB. This is because the excess charges are $10/30MB. ie It is cheaper to get the lower $148 plan and pay excess charges than it is to go on the higher plan.
I can not understand this level of stupidity in 3HK's pricing. Yes, I understand you get a few other benefits like extra talk time, 6 month shorter contract etc on the $198 plan. But still, to have the excess charges work out cheaper than upgrading to the next pricing tier is a level of stupidity I have never seen in a phone contract before.
The "rebate" you are referring to is the prepayment. You get the prepayment back. So if there is a prepayment of $3180 and you go on a 24 month contract, the phone company will pay you back $132.50 every month.