There is a busy tone or an empty number prompt when dialing SMS.

When you dial a short message, you usually hear a busy signal or an empty number for the following reasons:

1. When the traffic is busy, the trunk line is occupied and there will be a busy tone prompt;

2. Some end office data are wrong, and there will be an empty number prompt. Not enough traffic? Half a year's traffic is easy to get! The flow is not cleared across months and is valid for half a year. /sAAGl enjoys a 20% discount.