Debit orders keep going off for cancelled contract

We tried an LTE contract with 8ta but had practically no signal in the area, so cancelled the contract in March this year. A technician was sent out to prove we have no signal, and he also said the only course of action is to cancel the contract as 8ta cannot help us. I cancelled in March this year, and considering that 8ta never met their side of the contract because of non supply of expected service, expected that immediate cancellation is within my right. Since then, the debit order keeps on going off my account. I stopped it once, and 8ta then took it off immediately again! So, they have now taken over R4000 from me. I went into Fourways Crossing and sorted out with Mario there, who promised to sort it out and get the refund to me a month ago. Last night yet another debit order went off. I want this money refunded immediately.