You cannot cancel or delete your return already filed.If You want to make changes to your return after you have already e-filed, it can be done by filing a Revised Income Tax Return.

You're going to need the acknowledgment number of your original tax return and the date of e-filing to revise your tax return. 

Follow the steps on the screenshot-based guide to file a revised tax return:

https://cleartax.in/Guide/how-to-revise-income-tax-return