Can you provide more detail? The term 'Top up' usually refers to prepaid accounts, and the maximum single top up is 1GB of data
In the My Account section, you can see your prepaid transactions and usage to learn your status. From there you can see when your top up was applied, and the data consumed since. It is possible the text you received was due to the consumption of your previous data bucket.
If you are on a post-paid account, My Account will show your data consumption.
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