Where can I get a replacement SIM card

[Willster]

My father has a old phone and upgraded but SIM card don’t fit and needs a new micro sim where can I order one

[MI5 · Accepted solution]

@Willster 

You'll need to call customer service.
Numbers here Guide: Coronavirus Community Help and Support 
Or advice from an O2 Guru regarding a way to get through:
If you call 202, when it comes to the reason you are calling stay silent for 15 seconds and you will be taken to the keypad options.
Press 2 for Everything Else
Press 5 for More Options
Press 7 for Anything Else which will put you though to someone.
Say "Upgrade", "Lost/Stolen" or "Fraud" if you have to, to get put through to someone.

Or pop into your local O2 store.

It's free either way.

[Bambino]

@Willster You will be sent a sim card that you can adapt to the size you need. There is a difference between a micro and a nano sim. Make sure you know which one is the right one for your dad's phone.