When the bandwidth limit exceeds, you can easily change the bandwidth usage of a domain by following the steps given below.
1) Login to Web Host Manager (WHM)
2) Search as "list" in the search box. From the search results, select List Accounts
3) Click on "+" icon near the respective domain for which you are going to change the bandwidth.
4) Click Modify Account.
5) In the resulting page, set your bandwidth.
6) Click Save to update the bandwidth changes.
7) Enable "Keep this account on package" radio button and click Proceed.