Knowledge expansion:
Each credit card master card can apply for up to two supplementary cards, and the master card holder has the right to request cancellation of its supplementary cards. The credit limit of the secondary card shall be designated by the cardholder of the primary card independently, and shall not exceed the credit limit of the corresponding primary card; If the cardholder of the main card is not specified, the credit limit of the auxiliary card is the same as that of the main card.
All transaction funds, corresponding interest and expenses of the secondary card are included in the account of the primary card, and the cardholder of the primary card bears all repayment responsibilities. However, the primary cardholder and the secondary cardholder shall be jointly and severally liable for the debts owed.
References:
Can a credit card be used as a card? Generally, the original card needs to be used for more than 6 months-People's Network