Hi there @Nobuu 

When you change your rate plan during your bill cycle, the amount of data and minutes you get access to during your first month of your new rate plan will be prorated. This means that you won’t have the full amount of your data until the first day of your next bill cycle (the first full bill cycle with your new rate plan). For example, if you switch from a 6GB rate plan to a 10GB rate plan with 12 days left in your bill cycle, you will have access to 4GB of data for these 12 days (10GB/30 days x 12 remaining days). You will have access to the full data amount once you start your first full bill cycle.

Hope this helped. 

Cheers,