Practical Ethics + Comcast

Being in a new apartment, one of the things that I had to sign up for is internet access. The only option I had was Comcast, so I called them up and place an order. After a few days, a technician came an installed the modem, and the internet has now been working for nearly 2 weeks.

I received my first bill in the mail over the weekend though, and I find myself in an unpleasant situation. Over the phone when I ordered, I was told that the internet service would cost $29.99 a month, plus $4.99 a month to rent the modem. On the bill I am being charged $6.99 for the modem.

I called up Comcast on Saturday, and asked about it. It turns out that on April 1st (no fools), the price of the modems went up, but the phone operator told me incorrectly. Now, this is obviously their fault and not mine, I should be allowed to pay what I agreed to on signing up. However, they are refusing to offer me the $4.99 price, hinting that I can take it or leave it at $6.99.

I'm not sure what to do. I'm being scammed, but at the same time, I'm only going to have the router for 3 months, so I'm being scammed all of 6 bucks total. The alternative is to return the router, and go find my own at Best Buy, for something like 80 bucks. A situation of practical vs theoretical ethics, do I let a company get away with scamming, when do so actually costs me Less than not?