You mean this?
After activating your SIM, you will get 1GB of data for 7 days to try our network. Once you’re happy, you can buy your first plan and enjoy the full benefits of 48.
Did you successfully activate your SIM?
Did you configure your APN settings correctly if they aren't configured automatically?
(Note that the free 1GB of mobile data is 4G only, not 5G).
Other than that, after activating your new SIM and installing it and getting it working in your unlocked phone only incoming calls and texts will work until you buy a monthly membership plan.
What exactly is/isn't working for you and what isn't as you expected?
If you need to contact 48 support about this then see the links in my signature below.
