Discovery Insure neglected to cancel my Insurance in time for debit run

My broker submitted my cancellation on policy *** on 20 March. Today is 2 April, and its still not cancelled!!! Meaning I will pay for my new and old (Discovery Insure) insurance. Ref ***. Discovery Insure’s negligence will cause that some other premium will bounce, incurring more costs. Compelety unacceptable!!!