What's the problem of insufficient SMS residual traffic?

There are two possibilities, one is the phenomenon of charging fees at random, and the other is that the traffic is too large, and you didn't open the superimposed package, so he directly deducted the balance of the money. If you really want to know what's going on, call customer service to find out. If he refers to the traffic problem, ask him to tell you the flow of traffic use and when a lot of traffic is used, resulting in downtime. Because the customer service is from the company, he has to speak for the company. Don't ask anything, then you will suffer.