Answer call after 15 min then mutes headset on the

I closed my account at the Centurion Mall branch about two months ago. Yet, I still receive statements advising I have 37c credit. At the time, I explained to the store lady that they should please write this off and close the account. When I called at 11:47 today I had to hold for 15 minutes before someone answered. The lady who answered then pretended not to hear me and quite possibly \muted"her headset so that no sound could be heard on my side. People who have knowledge of call centre systems understand how this works. Meanwhile my cellular phone continued ticking time away"