Old phone number not transferred to new SIM

[Agar1997]

I am trying to get my new O2 SIM working with my old phone number from a different network (Three). I activated the SIM today, since the service on my old SIM stopped, but the SIM I'm using is using a totally different phone number. I was supposed to be able to use my old phone number by 6pm today, but it hasn't worked even after resetting my phone. Any advice would be appreciated!

[Bambino · Accepted solution]

@Agar1997 Did you give O2 your PAC? Migration & porting into O2 - O2 Community

If so, you will need to speak to customer service.
Call 202 from your mobile or 0344 809 0202, 0800 902 0217 or 0800 032 1402
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 the suggestion above doesn't get you through.
Best time to call is 8 am.
You can also reach O2 via social media:
Facebook (https://o2uk.co/O2CFB), Twitter (https://o2uk.co/O2CTW), or Instagram (https://o2uk.co/O2CIG)

[Agar1997]

I gave them my PAC code in-store when I bought the SIM last Friday so I'm not sure why it's still not working now. I'm actually struggling to call O2 because I have no cellular service and the numbers you provide aren't available via WiFi calling at least from what I can figure out on my phone. I feel frustrated just being left in limbo while I don't have access to any other means of telecoms...

[Agar1997]

Update: My number has now fully transferred, it just took slightly longer than expected! Thanks for the advice anyway