No, you don’t need to pay the full price when upgrading to a higher plan. Since your current plan is still active, the value of your unused days will be prorated and deducted from the upgrade cost.
The exact amount you pay depends on how many unused days remain in your current plan, and the system will automatically calculate this for you.
Please note that while the pricing/checkout page may display the full price of the new plan, you will only be charged the price difference at the time of payment.
After upgrading, your new plan will start immediately from the upgrade date (not from your original plan’s start date). For future renewals, the subscription will be charged at the full price of the new plan.