I am a Xiaomi mobile phone customized by Unicom. I have been receiving text messages saying that my credit line is not enough for 50 yuan, and then I charged 100 yuan.

It's not the phone. If you don't customize many paid services to make rational use of traffic, there should be a problem with the package.

What the staff in the business hall told you should be to save money and send a mobile phone, provided that the mobile phone is equivalent to giving someone away in two years. The money you pay is equivalent to your expenses, isn't it?

You need to be online for two years, that is, it takes two years for this number to be changed or not used. The cost should be a fixed amount returned every month according to the signed contract, such as 70 or other amounts per month. If your total monthly expenses are lower than this amount, then you should not be in arrears. If your monthly fee exceeds the refunded phone bill, you will be in arrears at the end of the month. At the beginning of the month, you will be notified by SMS that the credit limit is insufficient and needs to be recharged.

Suggestion: Call the customer service of Unicom to find out how much phone bill you return each month, and then plan your calls, text messages and Internet traffic according to this reasonable amount. If you control it, you don't need to charge it. Understand?

Not an official answer, hehe.