Terrible return/cancelation process with Mtn

It is with regret that I have to share this ,at the of June I returned the router to Mtn as it was longer required by ourselves .Bearing in mind that at that point because of Mtn 's safety net billing we had already paid Mtn up until the end of August 2024.When the guys at store (Musgrave Center ) actually return it to factory has nothing to do with me .It was confirmed that we would not be billed on the 4th of July however the debit still successfully went off .We left that debit because of the 30 day cancelation policy which because we had paid so in advance did not make sense .Mtn then proceeded to debit me on the 4th of August which I then reversed as I cant pay for a device which I am not using . I have since received a notice advising me that I need to pay a debit order or it will affect my credit record ,how is this even ethical ?

This treatment has been shocking to say the least and truly hope that this is resolved soonest .

Regards Ilza Swartz