I also thought that this was a case.
Only last week, I decide to start paying Panda for bin services by DD.
I rang, and Panda took my bank account details. I assumed that I would be sent out a DD mandate to sign, but nothing happened.
I checked my bank statement online yesterday and there was a DD payment to Panda.
I have not contacted the Permo yet to ask why they set up a DD without my signature. I'll let you know what happens.