Heading to the US anytime soon? You might want to pack a phone with a Three SIM in it.Three is extending its 'Feel At Home' proposition to the USA, Indonesia, Sri Lanka and Macau. Now I don't know your travel habits, but I'm guessing the first of those is perhaps the most relevant. Head Stateside and you can use your UK allowances for data and text and to call home and receive calls. Nice. Feel At Home is already available in the Republic of Ireland, Australia, Italy, Austria, Hong Kong, Sweden and Denmark.Commenting on Feel at Home, Dave Dyson, Chief Executive of Three, said: 'We want customers to get the most out of their devices at home or abroad. High roaming charges stop people enjoying their phones while they’re away and Feel At Home is the antidote to that.'Adding the USA to the mix is great news for our customers and shows our commitment to giving them the best experience in what is a popular destination. We plan to add more countries to the mix soon.'In related news, Three has confirmed that its total active customers figure now sits at 7.8 million - a 9.7% increase since Q3 2012. Three added close to 300,000 new customers in the most recent quarter.The network also confirmed its 4G rollout plans. From 2 December, Three started upgrading customers with a 4G-ready device, so they can access the latest high-speed data technology when they are in an area with 4G coverage. This rollout will accelerate in January, with all customers with a compatible device able to access 4G at no extra cost by the end of Q1 2014. Just as long as they are in an area with 4G coverage. Three aims to cover 50 cities with 4G by the end of 2014 and 98% of the population by the end of 2015.