Thousands of Americans have pledged $9 million to Haitian relief agencies this week by punching a code and sending a text on their cellphones. But it could be weeks, if not months, before any of that money actually can be used.

Secretary of State Hillary Clinton, CNN, and users of Twitter Inc. have urged people to punch 90999 and then type in the word "HAITI" on their phones to send $10 to the American Red Cross. But the money won't be routed from most U.S. wireless carriers to relief efforts until cellphone users pay their...