Hello, Kieran.
Welcome to Microsoft Community!
There's a pretty straightforward way to determine if your Surface Pro 11 supports 5G connectivity.
You can simply check to see if the Surface Pro 11 has a SIM card slot:
Insert a SIM card into your Surface - Microsoft Support
Here you can analogize the Surface Pro X installation demo image:
If you are unable to locate the SIM card slot, your current device is not 5G capable. You will need to check with your retailer and decide if you want to apply for after-sales service.
I hope this information helps.
Best Regards.
Leo.L - Microsoft Community Support Specialist