If you have Telia Mobil Obegränsad with unlimited data and if you got that from April 1 or later, you’ll automatically have access to 5G. If you have another subscription, you’ll most likely need to change. If you have the option to turn on 5G in the mobile network settings, you should be able to use it with 5G in Sweden. If you use dual sim, it probably won’t work. You won’t need a new sim.