Fnb in Jabulani mall mistreat me

I have a cheque account and a savings account with them. I have 2 kids, they both have savings accounts with fnb too. My daughter is 10 yrs, my son is 5 yrs. I recently saw that my son's account was closed and called the call centre to find out, they referred me to the branch. I went to Jabulani fnb bank and they told me that my child's account was closed because the last transaction was on the 31 July 2020. I explained to the guy who was assisting me that it's not yet 3 months hence I dont understand why would they close that account. He was rude and told me that the account was closed on the 5th of this month and they even count the month that the transaction was last made. I asked him to reopen the account cause I still want the same account number, he said for them to reopen the account I need to start from scratch and bring my son's birth certificate and proof address. Told him I dont have any proof of address as i no longer have clothing accounts, not unless I withdraw my bank statement from fnb and use it as proof of address since I'm banking with them and they still have my details with them. He said no, I told him that it's not a new application and I can give him the birth certificate and my ID to reopen it. He told me to go to the municipality and ask them to give me the proof of address cause he won't assist me without it. The service I got was unpleasant and draining. How can they treat me like a new client while I've been banking with them for long. Consultant didnt even have a name tag, was untidy and rude.

I'm thinking of closing my account with them, the treated I got was cold.