Supplier taking unathorised DD's

Client has noted a supplier [ of their broadband] has taken 2 identical direct debits, within a couple of days - transacted six weeks ago and refuses to discuss or refund 

What is the current view on this [ nb the hassle of moving a broadband supplier is not worth the sum involved ] ?   and what compensation would you normally consider in such circumstances  ?

Given that it has been over a month since the last 'help yourself'  they clearly have a lack of internal controls.........,  but to stop the next DD will result in some invoice chaser [ rather than account handler ] suspending the vital service

Seeing this happening more frequently and the DD system and lack of contact other than email is so frustrating

Thoughts appreciated