[Galaxy Note GT-N7000 General] Jade Eyed Wolf:
I recommend changing your account's SOC code only for the sake of consistency, and because of the fact that AT&T can see that you're no longer using an iPhone with a plan specifically designed for that device. Thus, they may either change your plan automatically anyway, or you may run into service issues. By calling in to customer support, you're just being proactive in this process, and possibly avoiding headache down the road.

Now, having said that, 7mbit down in the middle of an urban environment seems pretty normal to me actually. There are many factors to consider when it comes to the actual usable bandwidth you'll see, and it can vary quite a lot depending on those factors.

For instance, something to consider is the difference between connection speed, and user throughput. Lemme explain:

Connection speed simply indicates what the device is able to process in total at any given moment, including things like overhead. So, in other words, even though the Note has a maximum possible connection speed of 21mbit on the downlink, you're very unlikely to actually see 21mbit of usable bandwidth because that figure also accounts for the aforementioned overhead. Maybe, under the most ideal conditions, you could theoretically see a maximum of 18mbit of usable downlink (I'm just pulling this number out of thin air mind you) because the remaining 3mbit is reserved for things like protocol encapsulation, error correction, re-transmission attempts, etc.

Another thing to consider is the difference between signal strength versus signal quality; they aren't the same! You could have a very strong, but also very poor quality signal in the middle of a city, and still get lower performance than, say, a very weak but very high quality signal out in a sparse rural area.

Being in an urban environment, you'll likely have many more buildings which create echo's and reflections, and also you'll likely have many other devices nearby which are all broadcasting signals of their own, thus creating signal interference. Those all reduce the signal quality. Error correction kicks in more often, re-transmission attempts rise, your data overhead goes up, and thus your usable bandwidth goes down.

Finally, for each cell tower, you are one out of possibly hundreds users all competing for the same connection. Imagine your home WiFi for a moment. Everyone connected to your WiFi in your home is sharing a single connection to the internet. Thus, there may be a noticeable dip in performance when someone starts playing an online game, or streaming a video, or downloading a really big file, etc. Each cell is kinda like that, but on a much larger scale. Basically, each cell has a limited amount of bandwidth it can use for providing service to the people connected to it. This is the network's backhaul. Some cells have more backhaul than others. Either way though, the more people connected to a particular cell, the less backhaul there is to go around. So, being in a city, where there are more users per cell than in a rural environment, the less backhaul there is for you to use.

So, the next time you decide to watch YouTube on your Note, take a moment to imagine all the extremely complex things that are happening in the background to make sure you enjoy your video! It is a truly wonder piece of technology that you're holding in the palm of your hand!

Hope this has been informative! :)