CellPhone Banking ****mmmmmm

I was making an ewallet transaction via cellphone banking, entered the number then got a prompt "We notice you are sending money to an FNB account holder. Please note it will be cheaper to use Pay 2 Cell". After seeing this I took the advise from FNB to do a cheaper option of Pay 2 Cell. It is my bank after all I trust them. Unfortunately the person I was making the payment to informed me after that they had closed the account meaning they can't access the funds. I requested FNB to reverse this amount of R1 500 due to this error, I was informed that I will be charged a penalty of R325 for this to be processed of which I reluctantly obliged. They gave me a form to fill in and send to the reversals department of which I did. I am shocked to get a response stating that the account has insufficient funds therefore I should forget about getting my money back. In essence, I paid money from my FNB account to another FNB account while using FNB's prompt system but FNB is not able to recover this money which we know exactly where it went(into an FNB account). Please make this make sense to me so I know where I stay with FNB who I've been banking with for well over 10 years. If FNB is not willing to get my R1500 back then I will have no choice but terminate my relationship with them as I cannot trust that my money is safe with them.