If you have a reseller account, then you can limit the bandwidth usage for any of the accounts of your customers. You can get it done from within your WHM.
Here are the steps you’ll need to follow –
1. Log in to WHM.
2. Click on Limit Bandwidth Usage under Account Functions.
3. Select the domain from the list.
4. Click on Limit.
5. Change the bandwidth and click Change.
That’s how you can change account bandwidth in WHM.