I recharged, but I got a text message that my data(or plan) is done in 3 days.

I recharged, but I got a text message that my data(or plan) is done in 3 days.

1. Data 
Our prepaid plan offer limited LTE data and when you use up, you can use the 3G unlimited data. 
The text message about data is for LTE data usage. 
When your LTE data ran out, you can use 3G data. 

2. Plan
When the period of use is 1 or 3 days left, the notification text message will be sent. 
This is an automation reminding text messages and if you recharged already, you do not have to recharge again.