Three premiums deducted in 1 month

In November 2014 I applies for a car insurance and my agreement with you was to pay R1800 per month. In December 2014 three premiums were deducted from my salary (R1800x3=R5400) and they reflected as Advance premium. To my understanding only two premiums were supposed to be deducted! The January 2015 and February 2015 premiums were deducted accordingly. <br> <br> I cancelled this policy end of February 2015 and I made an application for a refund of R1800 but to my surprise only R400 was refunded yesterday.<br> They must refund me the outstanding value!<br>