Having read the advice online that buying a sim card in town would be cheaper than getting it at the Heathrow airport , I thought if paying a bit more would save me the trouble of finding a mobile shop in central London, I don't really mind. So I went to the Sim Local in terminal 1, got a sim card with a 30-pounds vodafone "3GB data+ 1000 mins call + text messages" bundle plan that the staff assured me to be enough for my 12-days stay in UK. I had the staff to activate the card for me before I left the shop. It was fine at first but unfortunately it stopped working after one day. I couldn't use the internet, I couldn't call, I couldn't send messages. When I try to call, I would hear a voice message saying that I have no "credits" left. The staff in Sim Local told me that the plan I joined was vodafone, but when I rushed into a vodafone shop in town to seek help, they told me the sim card was a Lebara sim card, and even though it's using vodafone network, they have nothing to do with the plan I signed up for. I tried calling Lebara's customer service, but I couldn't get through to any operator after much waiting. I went to another mobile shop to seek help, and after having them checked the sim card for me, I was told that the sim card had run out of credits, probably because the bundle plan was not set up properly so everytime I used the internet, it was deducting from the amount I paid. Basically he said the person who set up for me didn't do it right, and I wasn't using a bundle plan. I had no other choice but get a new sim card and joined a new plan which I used for the rest of my trip without problems. Just before I left the country, I went back to Sim Local on terminal 1 and found the same staff who sold me the plan. I explained everything and he checked the sim card for me. He said it should have worked and there was no way that I couldn't use it after 1 day. But I told him that was what happened. I said I wanted a refund but he said he couldn't do it and the manager was not around. He insisted that he set up the phone correctly for me and he had no idea why it didn't work, and even though he agreed himself that I wasn't using the plan I signed up for, I did use the internet and used up the credits so he couldn't give me a refund. I just find it totally unbelievable that I would encounter something like this inside the Heathrow airport. Seriously I would never try to get a sim card at London Heathrow again. If you buy it in town and you get a problem, at least it's easier and less time-consuming to go back to the shop and have them checked for you.