Edgards won't pay me back

I had an Edgars account a few years back which i paid up and closed. Sometime in 2019 i started receiving calls from the Edgars call center. Firstly the agents did not want to confirm why they were calling me as they said they needed to confirm they were speaking to the correct person. My question was " you called me on my number and now you want me to confirm my personal details to confirm its me?" I started ignoring the phone calls, so they started bombarding my brother with the phone calls telling him they need to speak to me. So i finally give them a call to find out what they want from me and i am told that i over paid my account when i closed it and Edgars owes me. I am told I should go to my nearest Edgars store with my ID and they will assist me. I go to the store and they tell me that since my account is closed they cant help me. I need to send some documents ( ID, Bank statement and request letter) to their head office for the refund. Today i called they head office to further inquire. I ask the consultant i was speaking to, to explain to me why i need to send my bank statement? Is it possible for me to send them an account confirmation letter? she is not able to give me an answer to my question. I ask her what happens if i do not want to share some details on my statement and she tells well then you will not get your money. My question is why must i share these personal details with Edgars? I am not the one that owes them they owe me