MediaMax vs. iPhone data plans

Okay, here's the lowdown.

Originally, I had a Nokia N95 with the MediaMax 200 + Unlimited M2M text messaging Plan and this was for $25 a month.

Now that I switched over to the iPhone, I was forced to change to the iPhone data plan which is just pretty much unlimited data + 200 text. This is the same as the above plan I just mentioned but W/O the Unlimited M2M text messaging. This goes for $20.

I've been looking over AT&T text messaging plan and if I wanted unlimited M2M, I have to add-on the 200 + Unlimited M2M text messaging plan which is $10.

I was wondering if anybody know if it's possible to NOT use the $20 iPhone data plan and go back to my MediaMax 200 + Unlimited M2M Texting plan? This will save me like 5 dollars a month...which is a good $60 a year from now. I mean, is there really any real differences between the MediaMax and iPhone data plans?

I can't seem to find a way to remove the iPhone data plan on my account when I log into AT&T's website. I'm planning to call them up tomorrow and say something like "i returned my iphone...i want my mediamax plan...blah blah blah". What do you think?