Porting Fnb back to Vodacom

My dad want's to port his Fnb connect sim back to Vodacom. He went to Vodacom now 3 times. He phoned FNB Connect twice and they said that they released his number, but by the third time with no luck porting back to Vodacom they told him that it is not possible to do that and the only way is to get another number. This is a huge problem because I also need to do the same because of reception at my business, and this is my business Tel no. I started reading up on this matter and with a shock I see that it looks like it could be true, for there is other customers that has the same problem. HOW IS THIS POSSIBLE? I don't have good reception where I am at the moment with FNB. What should I do?? Is it not my Constitutional right to use the service provider of my choice??? I thought FNB was awesome and I moved all my accounts to them, but now I don't know so much??