We bought the train tickets at the Kaili window, from Macheng to Harbin, for the T182 on July 19th. Afraid that the train might be late and I might not catch it, how can I change the ticket on my phone?

You need to go to the window to change the ticket, you can try calling the customer service hotline.
You need to go to the window to change your ticket, you can try calling the customer service phone.
You need to go to the window to change your ticket, you can try calling the customer service hotline.
You need to go to the counter to change your ticket, you can try calling the customer service hotline.