Proof of address not accepted

So I tried today to update my address details as FNB Barberton. I had my fibre bill (as this bill was accepted for all the other times that I have had to FICA myself). They would not accept it. They asked for a bank statement of another bank (which is ironic because surely they would want to keep money at FNB) or a municipal account (which is impossible as the house is not in my name).

Now please can you educate me as I looked online and it states clearly that any bill (be it a clothing account, a bank statement, telephone, fibre, etc) will be accepted, so why is FNB Barberton being difficult?

I opened up a Discovery Bank Account before typing this, and they have accepted my fibre bill as proof of address.