Cant process payments error 133 recipient reference invalid

I have been struggling for two days straight to make payments on my internet banking. i keep getting error code 133 which says the recipient reference i used is incorrect. i tried once-off payment/public recipient and immediate payment but all comes back with that error. how on earth is that possible because i use my MTN ACC NO as a reference to make payments. i have done it with all the other banks and it works perfectly fine. I cant change the reference as the company i am paying wont be able to know its me paying without the correct reference which is my account number or cellphone number ( none of the two are working). I was about to move my salary so that i get it on the FNB Account and was promised a cashback but i will not do that since i am already struggling with making a simple payment. Secure chat not working. i called in, spend 59 minutes on a call with Cwangcisa Xinindlu who did her best to assist but couldn't. she promised i would get a call back from the manager and have since not. this is NOT CONVENIENT BANKING.