Port my number does not work

I have been trying to port my number from FNB to MTN all week. FNB sends me an OTP and says to dial *147# and select port my number. This option does not come up on the menu. I’ve been on the phone all morning with the call centre and not one person is able to assist. I get told to dial *147*5*2# but it just says invalid number. The call centre staff just tell me there’s nothing they can do I must just keep trying to dial the number. Do not take a SIM card from FNB if you ever want to port your number to another provider. You will be stuck with them!