China Unicom’s online business hall may not support it in some cities and towns. In most cities and towns, iPhone 5s can be purchased through installment payment. You can select your region and click on the mobile phone product of your choice. If you support installment payment, you can have the words "Instalment Payment" in the lower right corner of the mobile phone picture. As shown in the picture:

In addition, it should be noted that installment payment requires a credit card, and not all banks can accept it. Only relevant cooperative banks are required to support payment. You can click Installment Payment to view supported banks.