It's not possible to update the price, billing frequency, etc on a published membership. However, there is a workaround for updating a plan.
This workaround is useful if you:
published a membership by mistake and need to make updates to the price, billing interval, etc.
updated your pricing.
want to manually change a member's membership.
Step 1 - Archive the old membership plan & remove any signup links from your site.
Step 2 - Create a new membership & add the new signup links to your site.
At this point, you've effectively "updated" the membership. However, archiving a membership isn't going to affect members who already signed up. To update their memberships we recommend the following:
Step 3 - Issue credit in Stripe equal to the new membership price and ask your members to "upgrade" to the new plan. You'll need to explain that you updated their balance so that they will not be charged. Here is an article on how to issue a credit in Stripe: https://stripe.com/docs/billing/customer/balance.