Welcome to the Community Forum, I'm sorry that your 3G isn't working. Apologies as well for the delay in getting back to you on this. Are you still having a problem with this, or has the 3G started working again for you?
If you are still having a problem with this, please let me know. I'll need to take more details from you in order to look into this, so I'll send you a private message requesting further details. Just check the envelope icon at the top right of this page.
Need help changing SIM card? Find out more about activating your 4G ready SIM. 4G SIM Swap Help