My trial period has finished, how can I access my account and subscribe now without losing my data

As long as you have your QuickBooks Online login credentials, warsame-abdullah, you can access your account. 

QBO keep accounts that are canceled or inactivated to be accessed within a year for viewing purposes only. To subscribe again, let me show you how: 

1. Log in to the QuickBooks website. 
2. If you're prompted with the Account and Settings page, click Subscribe. 
3. If not, click the Gear icon at the upper-right.
4. Select Account and Settings. 
5. Click the Billing & Subscription menu.
6. Select Subscribe. 
7. Follow the on-screen instructions until you'll finally be subscribed to QuickBooks. 

You can refer to these articles that will help you manage your sales and expense transactions. 

I'll be here if there's anything else that I can help you with. Thanks for subscribing to QuickBooks!

My trial period ended & I added my credit card information to get the 1 years subscription at 1/2 price for switching from Quickbooks Desktop to Quickbooks Online.  I did not know they put in the Advanced plan and after I added my credit card information they will not let me change to the Plus plan I wanted without losing my discount.  This is terrible customer service & very deceptive.  I did not enter the Advanced Plan into my Billing & Subscriptions or ever intent to take that plan.  

Beware of these deceptive tactics when  you are subscribing after the free trial period.