FNB changes bank account type WITHOUT consent / authorization to charge higher fees

Good day

I just realized that someone at FNB changed my Business Zero account (no monthly fees) to a Business Gold account WITHOUT my consent or instruction. This resulted in banking charges raised to R 140 on the Feb statement and R 176 on the Mar statement (my avg fees for the 6months before that was R8). This is unacceptable. I called to enquire and all that the consultant can say is that he mailed the person who changed the account. This is not acceptable. What if I did not check the statement and FNB overcharged me every month. I want immediate explanation on this please and my bank charges refunded.