FNB Connect don't know what they are doing

I bought a device on FNB connect over 2 years ago. I was overcharged through increased debit orders as well as that they continued billing me for additional months even though the device was already paid off after 24 months. When I laid a complaint they came back to me and said that my payments only started in June but I showed them proof in my bank statement that it started in April. Do these guys not know what they are doing? This is seriously concerning that I have to show my bank my bank statements to prove payments went off. They said they are going to look at the contract and share it with me, but they just went silent.