@havoc Which phone is that? Go to network/SIM0 settings and you should see an option for 5G. Check if the handset is compatible and if the mfr. needs release a firwmare that makes it 5G compatible. 5G is visible as an option on OnePlus.
This is my moto edge 20. I tried it on edge 20 pro & G71 as well but 5G only option is not there. I also have LG wing which also shows the same 3 options. I guess it's just like this until the phone detects 5G wireless signals.
@vishalrao I have both old and new sims. I think it's just that whenever our phones will detect 5G signals near them they'll show the option. Or if it is available then they'll automatically switch to 5G and will show options. Some people went to US with their moto G71 device and got 5G there and shared speedtests. So yeah 99% this is the case.