How do i want to delete all my previous company's data? Because i already upgrade new plan to use it for my new company.

If you are using QBO Simple Start or your account > 60 days old, you should open a new account and cancel the old one.

https://quickbooks.grsm.io/Asia-Pacific

Hello there, pkrcstemerloh@gm.

You can follow as what Fiat Lux - ASIA provided work around. 

Also, you can still delete it if your QBO data is less than 60 days old. I'll guide you on how to reset your company:

1. Log in to your QuickBooks Online account.
2. Edit the URL on the address bar. Remove everything after app/and enter purgecompany. For example: https://...qbo.intuit.com/app/purgecompany
3. Click Yes to confirm the action.
4. Select  Wipe Data.
5. Once the deletion is complete, you will be rerouted to your home page.

However, if it's active for 90 days or more, cancel your account directly on your QBO profile and start a new QBO account. Here's how: 

To cancel an account:

1. Go to Gear icon and select Account and Settings under Your Company.
2. Select the Billing and subscription tab.
3. In the QuickBooks section, select Cancel.
4. Follow the steps to cancel your account. If you use payroll, you should cancel your payroll account too.

To start a new account:

1. Go to https://quickbooks.intuit.com/choose-country/.
2. Fill up the User ID and password.
3. You can use the same user ID and a password you previously had. If you activated payroll in the account, this is the best option for you.

You can read this article for additional reference: Delete your data and start over in QuickBooks Online.

For more insights on what will happen to your data if you cancel an account, you can check this article : Learn what happens to your data after you cancel.

Let me know if you need further assistance. I am always here to help. Keep safe.