How to calculate the phone bill of Unicom?

Let's put it this way: You used to have 54.78 yuan in your card, with monthly rent of 66 yuan and SMS consumption 17.7 yuan. Later, you recharged 50 yuan. Let's set a scenario: such a deduction will happen to post-paid users. For example, at the beginning of the month, your card only has 54.78 yuan, then the system will display the available balance as follows: 54.78 yuan -66 yuan =- 165438. That is, you will owe 1 1.22 yuan. If you spend 17.7 yuan on the SMS, the debt will reach 28.92 yuan. Then recharge 50 yuan, and the available balance is displayed as 2 1.08 yuan. Unless you have other unclear expenses, this is the calculation method.