T-Mobile has announced that they will be raising the per-message rate from $.10 per message to $.20 per message. This is a material change of service, and as such, you can cancel service without paying the early termination fee.
Some customers have already confirmed success in porting their numbers out (or simply canceling service outright) using this reason. Some have been told that they cannot cancel service because they have a text messaging plan. However, one can raise the point that if they chose to remove their add-on in the future, they would be materially affected by this change.
The rate hike matches the rest of the industry, which has been progressively raising pay-per-use SMS messaging rates, in order to force customers to defensively sign up for a text messaging plan. With plans generally starting at $5, a customer will be losing money (compared to getting a messaging plan) after only 25 messages sent or received. With no way to screen text messages before incurring charges, many customers feel pressured to select these add-on plans, even if they do not regularly text message themselves.