Debit order after cancellation

In April I went to the Miway website to cancel my policy and that was done successfully,when you click cancel policy an email automatically populates then you send it to Miway,and that was done. Then last month I sent an email to my bank to reverse the debit order and stop it yet this month Miway saw that it was best to change their reference number and debit my account again,why for who and why? I sold the vehicle in April hence I cancelled why are you resorting to tricks to get money from people? Please refund the amount you have debited and I cancelled in April and thank you