When signing up for a new subscription to QuickBooks Online, you'll have two choices: a free trialor50% off for 3 months. Since you chose the free trial option, the discount won't apply to your subscription. In order to get that discount, you'd need to have signed up for the promotion initially.
Make sure to click the Buy button to get the discounted price for up to 6 months. If you purchase from the trial account, you have to pay the regular price. No data will be transfered from trial account.