Debit order Mandate- Norman Bisetts and Associates

I authorised a debit order mandate for Nrman Bissets and associates. What they did is they went and deducted the same amount twice and just changed the last digit on the reference number. I don't understand how they bypassed the banking system when the debit order mandate is supposed to work only on 1 reference. This is *****. When I tried contacting them via their whatsapp number and connect to an agent, then none of the selections work neither tha agent. It becomes impossible to reach them. But they phone you from 6AM even when you're in the toilet.