Every once in a while I see customers complaining about unjust data charges. My solution is simple and I've seen in put into place on certain European carriers already. If a plan does not include a monthly data allowance, then place you data block feature on the plan by default. When a customer signs up for your service, have your employee explain the situation (and that they need it enabled for MMS) and the customer is then required to authorize the removal of the block (and initial that they have elected to do so). Alternatively, they can call 611 at a later time to activate data. With this in place, a customer will not be able to say that a rep forgot to explain how data works. If the rep forgets to do this, then there will not be any surprising charges on that customer's bill because data is off by default.