In order to remove all costed services associated with a client account, you will need to remove / delete any allocated trunks, SIP clients and DDI's. The 'Delete' button will not be enabled until this has been done, as detailed below.
Step 1: Remove any trunks and SIP clients
Via the client's 'Trunks' tab select the trunk you wish to delete, right-click and select 'Edit' then 'Delete'.
Repeat for any other 'Trunks' and/or any SIP clients set up on the client's 'SIP clients' tab.
Step 2: Release and delete any DDI's
Via the client's 'DID numbers' tab, observe any numbers that are attached to any 'SIP accounts' (trunks) and if any are, right-click and select 'Release from trunk'.
Whilst still on the client's 'DID numbers' tab, select DDI's, right-click and select 'Delete from system'.
Step 3: Delete the client
There is no inherent cost in keeping a client account set up once trunks and DDI's have been revoved, only trunks and DDI's and any services associated with them such as Call Recording incur charges.
Via the client's 'Options' tab, press the 'Delete' button, which is only enabled when all trunks and DDI's associated with the client are first deleted.