Is it free for the main card and the auxiliary card to send text messages?

Guangdong Unicom's 3G family fun service costs 10 yuan/month per card. The main card and the auxiliary card can enjoy the resources (including voice, data traffic and short multimedia messages) contained in the main card package and the traffic superimposed package ordered by the main card. The foreign investment fee exceeding the package is charged according to the foreign investment fee of the main card package. Give away caller ID, ringtone and 10G version of my email address. Texting between the main card and the secondary card is not free, and it is charged according to the standard package fee.