You need to remove all balance before trying online.
And that means accrued interest also.
So, practical option is- on LAST DAY when Interest is credited, remove ALL balance, and next day call and request acc closure link. They will ask reason for closure and send SMS for the link. Fill it and it will be done.
If it is still not done, that means there is some issue with account- go to branch to close it. Don't be laggard for some work. 🙂