I want to upgrade the subscription for my company for one month from Simple start to Plus and then continue with Simple start.

You can upgrade or downgrade your QuickBooks Online (QBO) edition through the Subscriptions and billing page, harshofl.

Before changing your plan, ensure you're signed in to QBO as a primary or company admin. To upgrade from the QBO Simple Start edition to Plus, here's how:

1. Go to Gear icon at the top and choose Subscriptions and billing.
2. Make sure your payment info is up to date.
3. In Your Subscriptions, select Upgrade your plan below the QuickBooks section.
4. Review the available plans and then select Choose plan.
5. Follow the on-screen steps to upgrade your plan.

If you're downgrading from QBO Plus to Simple Start, be aware that you may need to disable some features. Especially, if you have the multicurrency feature enabled, you won't be able to switch back to QBO Simple Start.

For more information before changing your plan, I recommend checking this article: Upgrade or downgrade your QuickBooks edition. Then, visit the Downgrade your edition section.

If you want to update your credit card or bank account details in the future, you can check out this article for a gudie on what to do: Manage billing, payments, and subscriptions in QuickBooks. This also includes information on changing your billing schedule.

If you have further questions about changing your QBO plan, feel free to ask. I'm here to help!