Hello, please can someone give me a quick primer on global GSM phone bands? Recently I was in Ireland, before I left I bought an unlocked GSM phone to use there. From somewhere I read that "Three Ireland" was a good service with a €20 unlimited everything plan. Unfortunately both me and my friend using a Galaxy S6 had poor service. He had text and voice at all times, but no data, but that might have been because it didn't turn on roaming for data. I had slow data in the country as well as text and voice, but in Dublin proper I had nothing what so ever. From what I've read maybe we were roaming on the Orange network on 2G. Then I got a Lycamobile Ireland SIM and signed up for a €10 more limited plan that generally worked. I think I was on G3 because the internet was usable. So that leads me to wonder if it was not Three’s problem for the crappy service, but maybe my phone. It looks like maybe my phone doesn’t have the same network settings that Three has… My phone: • GSM Quad Band 3G/4G HSPA+ (850/1700/1900): US Compatibility Nationwide on all GSM Networks including AT&T, T-Mobile, Cricket, MetroPCS, Straight Talk and others • Unlocked cell phones are compatible with GSM carriers like AT&T and T-Mobile as well as with GSM SIM cards (e.g. H20, Straight Talk, and select prepaid carriers). Unlocked cell phones will not work Radio frequency summary used on the Three Ireland network Frequency Protocol Class 900 MHz UMTS/HSPA 3G 2100 MHz UMTS/HSPA 3G 1800 MHz LTE 4G So based on those bands does it mean Three’s crappy service was the cause of me not having a compatible phone? Could I expect my phone to work ok other places in the world? If I had an unlocked iPhone would it work better globally (they were selling iPhone 5C in Three store).