If you have bought a smaller plan and interested to upgrade to bigger plan, we have easy options for that.
Login in your account and go to this link.
You'll see an option that says " View Upgrades."
Click on that link and you'll see the available upgrades as per your license.
Select the upgrade and you'll be charged the remaining amount.
Here is an example to understand.
Let's say you bought a single site license in $49 and after using it for 6 months, now you want to move to 25 sites license.
In that case, you'll be charged $20 more (the actual price of 25 sites license is $69) and you'll be able to upgrade.