I didn't receive a text message after I changed my train ticket.

If you use online payment tools to purchase tickets through 12306.cn website, if the fare of the new ticket is lower than that of the original ticket after the change, the difference will be refunded, and the refund fee for the difference will be charged, and the current refund fee standard will be implemented. The refund will be returned to the original bank card or online payment tool used when purchasing tickets within the specified time.

Generally, it will be returned to the original payment card or account within 15 working days. If it hasn't arrived for more than 15 days, you can call customer service 12306.