psaus

Distinguished
Jun 13, 2006
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18,590
Often you can just go to the UK and the number will work. You may need to call your mobile provider to enable international roaming (quick phone call, should be a free setting.)
But as you said "Roam", it's likely to incur significant cost (unless you purchase a specific international roaming plan from your mobile provider).

My suggestion is when you get here buy a SIM card that has minutes and texts preloaded (will have a UK number). You can even get a phone for free or as little as £10 with these SIM cards. You might want the phone if your phone is locked.