If you downgrade your membership tier (e.g. from a "Pro" to an "Insider"), your new membership will start immediately and any remaining credit you have on your previous membership will be credited towards the cost of your new membership. Once your remaining credit has been used, your new membership will be renewed and you will be directed to pay your new membership fee.

For example:
If you decide to downgrade from Pro Monthly ($199 per month) to Insider Monthly ($99 per month) halfway through the month, the unused value of your Pro Monthly membership ($99.50) will be credited towards the cost of your new Insider Monthly membership. As the unused value of your Pro Monthly membership exceeds the value of the Insider Monthly membership, your next renewal date will be set for when your credit has been used in full (just over 1 month), at which point your new Insider Monthly membership will commence.

To downgrade your membership, head over to My Account.