Unauthorized Debit Order

I canceled my contract with Supersonic on the 1st of May 2020, I wasn't billed for June 2020 and I was billed for July 2020, I called Thursday the 2nd of July and was told someone will get back to me, I called again on the 6th of July, was given a 24hr turnaround period, up to now no one can explain to me why I was billed, one of my debit orders bounced because of this, now my credit score is tempered with cause of insufficient funds due to Supersonic, what does one do in such a case?

CAS - 117026 -S5S1D1