Banking details

I am so irritated. i changed my banking details 4 months ago with discovery(over the phone).... had a claim last week and they paid the disbur*****t into my old account (which i was planning on closing down... luckily i did not).. when phoning to find out why and what happened they said ohh well your banking details for the claims was not changed and that i need to fill out more paper work and supply bank statements..... WHY was i not notified of this from the start!!!..... if they told me this in the beginning when changing same i would have not made a fuss....