Acoount debited *******ly

I am ex employee of Nedbank who retired in 2013. Subsequently I took out an Admed Gap policy around 2004/05, I decided that due to affordability I cannot afford the monthly premium as it too high just like the government ripping pensioners off. I put.t a stop payment on the policy in December 2014, The debit was returned to me and again the debit went off in February 2015. I managed to contact a T Chauke at Guardrisk to cancel the policy. Now another R257.00 has been debited off my account with the excuse that I must give 1 month notice and premiums are for January and February. In all fairness I would like my money to be refunded. I have no correspondence advising me the do's and dont',s of the policy, I find this action shameful and disgusting!