obtaining PAC number I find it not recognised

What's not recognised? If you mean it doesn't recognise the date of birth you've supplied when trying to request a PAC via text, you're either supplying it in the wrong format, or you accidentally entered the wrong date of birth when you set up your Smarty account. You can instead get the PAC through your Smarty dashboard.

If you mean the PAC is not being recognised by the new network you're wanting to move to, you are probably entering it wrong. Note that the first three characters of the code are letters, while the remaining six are numbers.