FNB investigation is useless

I write yet again to complain about how fnb refuses to take responsibility for weaknesses in its system. R120 disappeared from my account and I don't know what I purchased, neither can they tell me what it purchased. Having waited for a week for their investigation, this is how they responded:

Dear M ***x

I herewith acknowledge receipt of your complaint: ***x

I received feedback from Credit Card and they have advised that you need to look at your statements and compile a recon.

Once done sent it to them so that they can see the amounts you noticed have been missing.

The R120.56 is the customers latest statement due on the 30/12/2023 and is not missing.

Yours sincerely *** FNB

Note that the amount disappeared without trace. How in the world am I going to show where the R120 went? This is not even my money that is being ****** it is the bank's money and now I am funding this bank. Is this how fnb makes money, by *****ing it from its clients and expecti g the clients to pay for it?