What should I reply if I transfer the secondary card to the primary card?

Reply "XZ sub-number" to 10086.

In the number portability service, both the primary and secondary cards can unbind the primary and secondary card packages by sending text messages, and then apply for number portability.

If the mobile network has a primary and secondary card relationship, you need to cancel the secondary card relationship first, and then handle the number portability service with the secondary card the next month.