We are currently on an annual contract and would like to switch to monthly billing for our upcoming renewal.

You can switch to a monthly billing by going to Settings > Usage & Billing > Subscription > Manage Plan.
In the checkout flow, continue to "Pay monthly or yearly, your choice" and select "Monthly". From there, continue to verify and confirm your changes.

Please note that this change will take effect at the end of your current annual contract. You can check the exact date in the “Changes” section on the right side of the overview:

Note: Our payment terms may be reviewed here.