No Response on Refund Due

On our request, our travel agent cancelled our airtickets Canada to South Africa for our flights in April 2016. The agent requested the refund 3 months ago and to date, we have heard nothing and KLM have not paid us out the monies due. We have given them our new bank accounts in Canada. When I queried this with KLM's Service Centre, they didn't read my email and just resubmitted my refund to credit my South African credit card account, which no longer exists. How can an international airline be so inefficient and take such a long time to do a refund with no feedback. Can't say I'll ever use this airline again - first experience with them has been a bad one.