Falsely accused of not paying for extension

I checked in to Southern Sun Maharani on the 29th December 2017. I paid on arrival. I was due to check out on the morning of the 2nd January 2018, but I decided to extend my stay for 1 more night. I went to reception and extended my stay, i paid in FULL & received my receipt and new room card after which i left the reception area. At 22:00, a lady by the name of Simphiwe called my room. My wife answered the call. She was extremely rude and asked how did we enter a room that we did not pay for? She then continued to say that there was no proof that we had paid for our extension and that we should go down to pay for the extension. My wife explained to her that that we had already paid in the morning, but she insisted that we come down to reception for payment. I am a cardiac patient and was absolutely appalled & distressed by the late phone call. I am a long time patron and i find it very disturbing that we were treated as *******. An absolutely stressful end to my holiday and don't think i will ever stay here.