You have the option to cancel a purchased number at any time. You can do this easily through the KnowRoaming App on iPhone, Android or at mobile.knowroaming.com for Windows Mobile.
To cancel your purchased number, open the KnowRoaming App to the "Services" menu and select the number you would like to cancel.
For iPhone , select the number you wish to unsubscribe from, then select "Unsubscribe this number"
For Android , select trash icon under the number you wish to unsubscribe from
Then select Yes to confirm number cancellation
For Windows Mobile, select the cancel icon next to the number you wish to unsubscribe from
Then select Yes to confirm