settled debt

Two weeks ago I Settled my outstanding amount via debit order. After the settlement amount was settled DMC once again deducted funds from my account. I contacted them and the lady confirmed that they will refund me and send me a paid in full letter. I tried to contact them on *** today without any luck. they also sent me smse that I promised to pay 3000 but did not honor the arrangement this after the amount was settled two weeks ago!!! This is such bad services. Can anyone assist me.