Three UK launched on March 3 2003 as a 3G-only carrier. Now fifteen years later, the company has decided to stop selling 3G phones and only offer LTE-enabled devices. It's the first carrier to make such a move. The 3G network isn't going anywhere for now, this is just preparation for the future. The carrier needs to wait until most of its users have a 4G-capable phone and until its network improves. Three's LTE network launched in late 2013 and it's not ready to fully replace its 3G network just yet. The US switched off its 2G networks, but Vodafone UK has committed to keeping them...
Source: https://www.gsmarena.com/three_uk_to_stop_selling_3gonly_phones_looks_forward_to_4g_future-news-31210.php
