Yes, upgrades are allowed within Digi Internet Freedom plans. Upon upgrade your bill will be prorated based on your usage of your previous plan and the new plan.
Digi Internet Freedom (Before 23 Feb) Support
Support Detail
Can I upgrade to a higher value Digi Internet Freedom plan within the contract period?
How do I upgrade my existing Digi Internet Freedom plan?
You may walk-in to the nearest Digi Store to upgrade your Digi Internet Freedom plan.
Can I downgrade my existing Digi Internet Freedom plan within the contract period?
No, downgrade is not allowed for Digi Internet Freedom plans within the contract period.