Go to Reports > Sales Reports > SMS (requires the Sales > SMS permission) and pick a date range. The report summarises sent messages and calls for the period and offers two detail windows: Total Purchased SMS Balance (every Bought By Admin and Auto Refill top-up with balance before/after, amount, method and time) and Total SMS Sent History (each Sent SMS deduction with a link to the message). For a per-message view use History > Sent and open a message to see its Balance History.