Changing mobile number after porting it onto a new SIM

Hi,

I have just received a new SIM (bearing a new number) after changing my phone plan with my provider. I had requested my old number to be retained so my old phone number has been ported onto the new SIM. However, it seems to me that the IPhone refuses to learn that my old number is ported onto this SIM now, in that, I cannot use iMessages or Facetime with my old number since it seems to have settled on the new one as the one I can use. I also checked to see what number it picks up in the phone information section and it is the new one there too.

I have tried signing out of iMessages, Facetime and signing in again. I have also tried to change my password as another person here had suggested. I tried changing it on the website. Nothing seems to work. Any help or ideas please? Thank you!