SIM cards from the 3G UMTS network onwards are backwards and forward compatible, and mobile phones are backwards compatible. So, a 5G SIM card will work in a 4G phone, but will only allow you to access 4G, 3G and 2G networks if used in a 4G phone .6 Kas 2019
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No, 5G sims doesn’t work on 4G phones .26 May 2018
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