You can easily remove a filter you created in Usage Analyst; you can't delete a shared filter someone else created. If you just need to make some changes to a filter you created, you can edit the filter (you don't have to delete it to change it).
Click Monitoring, click Voice Reports, then click Usage Analyst.
Select the radio button next to the account you want to view, then click LAUNCH USAGE ANALYST.
Control Center opens Usage Analyst in a new tab. (Depending on whether you have Bill Analyst or Usage Analyst set as the default view, you may have to click View: Usage Analyst in the upper-right corner, and select View: Bill Analyst to change views.)
Click the Setup tab.
In the Tools section, click Filters.
Select the radio button next to the report you want to remove the filter from, then click Remove Filter.
Usage Analyst asks you to confirm that you want to remove the filter.