REFUND - FOUR AND A HALF MONTHS LATER????

I cancelled my account with Chubb in December 2014. I received a letter dated 29 December 2014 confirming cancellation and informing me that because I need to give on month's notice, January 2015 debit order would still go through. I understood this but then February 2015 debit order was also presented. I have been trying to get Chubb to refund the February debit since the beginning of February. I have phoned, emailed and in the last month phoned 2 to 4 times a week. Every time I am promised that the refund will be in my bank in two days,next Tuesday definitely , tomorrow definitely !!! What must I do to get them to refund my premium?<br> .