Once the account is opened, you will see several icons at the bottom of the screen. Tap on the Account icon which can be found at the bottom right corner of the screen.
Once you tap on the Account icon, tap on the second option from the top in the following screen labeled as Investing.
Once you tap on Investing, scroll down to the bottom of the screen where you will see an option which says Remove Options Trading.
Tap on Remove Options Trading.
Once you tap on Remove Options Trading, a message will prompt on the screen asking you if you are sure to remove the options trading. If you want to continue with removing it, tap on Remove Options.