Standard Bank refuses to cancel a insurance policy

On the 5th of August my wife an ex staff member of Standard Bank contacted homeloans to cancel our <br> HOC policy as we took out another policy with DIAL DIRECT...they supp**** us with a email address which we were supposed to email a letter and the new shedule to...The message was only read on the 28th of August 2015 which resulted in a debit going through my account for Sept 2015. They then supp**** a fax number where we were supposed to fax the docs through to which we did...a couple of days later Webber Wentzel Attourneys phoned saying they wanted to cancel the bond...We clearly stated that we only wanted the insurance cancelled...Earlier today I got another email requesting the new shedule which i have now sent through 4 times...after a screaming match on the phone I was told that they will not cancel my insurance as the new policy is only for R900000 where the old one was for R2,400000..This propoerty is only worth R900000 and the bond has been paid up...in fact its in a positive balance...They cant explain why their valuation is so high....HOW CAN U EXPECT SOMEONE TO PAY AN INSURANCE INSTALLMENT FOR SOMETHING WORTH R2,400000 ON SOMETHING WORTH ONLY R900000