Hi Gokus, thank you for getting in touch to bring this to our attention!
You can have your mobile selected to whichever of the networks you wish. It sounds like if you would like to optimise your signal you would be best to choose 3G as this has the best signal for you. We are expanding our 5G network all the time - you can also check coverage in your area here.
Are you having any issues due to poor signal or signal coverage?
Let us know how you are getting on so we can offer you further support if needed.
All the best.
Molly