Q: Which sim do I use?

Put a new payg.sim in my inherited iphone. transfered my phone number from Orange to 3. Before loading with any credit, I decided to go back to Orange. Put £10 on a new Orange micro sim and got a pac code to swop my number back to Orange, only to find my iphone needs unlocking. Filled out an unlocking form, but submited the  wrong info. Did another form and got it wrong again, so my son helped me fill out a third. I have also called the help line and was told I will be receiving a text when it is unlocked. BUT which sim do I put in the iPhone or my old Orange sim/phone to receive the text.