What does SMS balance insufficient mean?

It means: a reminder that the free text messages are about to be used up

The SMS balance is the cost of sending you text messages. You will receive text messages when you use consumption. If you have not set up automatic payment, or your balance is insufficient. The text messaging function will be stopped for you.

Insufficient text message balance is also insufficient phone balance, because after the free free text messages are used up, corresponding service fees will be charged for each subsequent text message and will be deducted from the phone bill.

SMS is the most basic mobile communication service. 20 years ago, the world's first text message was successfully sent from a computer to a mobile phone on Vodafone's GSM network in the UK. Since then, text messages have entered the stage of the times and become an essential basic function for every mobile terminal.

For more than ten years, text messaging has been one of the Chinese people’s favorite communication methods. However, these basic communication services have not been upgraded for a long time. Their functions are single and the experience is limited. They can no longer meet the growing communication needs of users. Coupled with the impact from mobile Internet OTT and other services, the SMS service that was once regarded as the "thumb economy" is no longer prosperous.

Extended information:

The converged communication service that China Mobile is promoting is about to be launched. This service will transform traditional SMS and MMS into "new messaging" services based on data traffic, which means In the future, the charging system of charging 10 cents for each text message sent by mobile phone will become a thing of the past, and the billing based on traffic will be adopted instead. If this model matures, traditional text messages will undoubtedly enter the "free" era.