If you haven't published any memberships:
Head on over to the Stripe page on your dashboard, and click Disconnect.
If you have any paying members or published memberships:
You'll see an error that says "Please contact us to disconnect your Stripe account."
This is because Memberstack requires all active members to have a Stripe customer in a connected Stripe account. Any members that have currently paid will break because they are in the stripe account that got disconnected. For example, if a member attempts to cancel their account from the profile modal, the attempt will error out because Memberstack can't communicate with Stripe. This will be the case for almost any payment-related action.
To avoid these issues you'll need to:
Delete all paying members which will result in their subscriptions being canceled.
Disconnect your old Stripe account.
Connect your new Stripe account.
Have your previous paying members sign up again.