Here are the instructions to upgrade your plan:
1) Log in to your UpLead account.
2) Then click on your name or arrow on the bottom left corner, then click "Subscription".
3) Select the plan that you'd like to upgrade/downgrade to and just follow the prompts
That should do it.
Note: If you upgrade your plan, it will take effect immediately. Unused credits roll over to the new plan. You will also have a new billing cycle.
If you downgrade your plan, you will maintain the same access and features with your current plan until your next renewal date in which the downgrade goes into effect.