Despite the hefty price increase, Cingular customers will not be able to renig on their contracts. Sprint allowed users without a bulk rate SMS plan to cancel their contracts without an early termination free (usually around $200) after the price hike. Sprint did not reveal how many customers took advantage of that offer however.
Cingular will try to use this move as a way to get more customers to sign up for a bulk SMS plan. The base plan is $5 monthly for 200 messages and the top plan is $20 for 3,000.