cancelled policy - premium to be credited

I cancelled my home owners insurance with nedbank insurers at the end of February 2015. My bond instalment went of at the end of February including the insurance. It was then credited back into my bond account. At the end of March my bond instalment went of including the cancelled insurance premium. I called the call center and asked why my premium was not adjusted as I now have paid double premiums for 2 months and wanted my premiums credited back to me. I got long stories and promised that it will be done in 10 working days. This was on the 8 March. I had called 3 times after and each time was told that nothing was done with my mail sent and no notes of my previous complaints. All I want is my premiums paid back to me before the end of this week as I can not beg for money that belongs to me. The service from nedbank insurers is pathetic and extremely unhelpful.