I'm sure they'd rather keep you as a voice only customer than not be a customer at all...it's an unsubsidized phone after all.
To be blunt, not really. For every person willing to cancel over a data plan there are about a dozen others who may complain but ultimately are willing to either accept the plan or keep service and go to a different phone.
Besides, it's not like canceling does you any real good - all of the major carriers now require data plans on smartphones.
You shouldn't have to take a data plan, and if they add one threaten to take your business elsewhere. Explain the situation and keep asking for supervisors if the customer service rep isn't able to help you....worked for me.
Well let's be clear on one thing from the start - if someone did remove the data plan from your iPhone, they were in violation of policy, because what they had to do was actually remove the iPhone from your line and put in a dummy IMEI number so they could block the data. It violates policy, sure, but you could often get away with it in the past. They didn't start doing sweeps looking for phones in violation of the policy until the end of last year after the general smartphone data plan requirement came into effect, and for whatever reason didn't seem to do many changes to iPHones until the last few months. So if you're still using your phone without the data plan... it's quite likely that you'll end up getting a text message like the OP.
Call and talk to a supervisor all day if you'd like. Even if they block your data, next time the network sweeps your account, it'll slap the data plan right back in place. The sweeps don't give a crap about there being a data block on your account, they only care about the network IMEI that's reporting from the phone you're actually using. Now, if you were using any smartphone other than the iPhone you could
try to talk them into giving you an exclusion that would make the sweeps pass you by (it's meant for people who were grandfathered in on Blackberries and etc with no data plans before the policy change), but that exclusion doesn't do jack for the iPhone - iPhones have always been required to carry a data plan.