Yes, if you are a retail investor, you can cancel or modify your IPO application request online after you have submitted it. In case you can not modify it yourself, you can reach out to the broker on whose platform you applied for IPO and request for modification or deletion. However, it is important to note that the modification or cancellation can be done only till the subscription window is open. Once you cancel your application the funds will be unblocked after 24 hours.
Also note that for HNI investors, the option to modify is available, however, cancellation is not available.