Best unlocked phone with great reception?

I went to mexico recently with an unlocked phone. But to my surprise in some areas it did not get any antenna. Its an internal antenna phone. I was wondering if anyone knows which is the best unlocked phoen to buy that gets the graetes reception anywere. I mean anywere. If anyone knows of any phone that gets the best reception anywere. I heard nokias are good but i dont know. Can anyone please help. Tell me the brand and the number for it.

Note : Unlocked phones are very expensive to buy . Better, you can buy a carrier locked phone and unlcok it by using unlock code . You can get it from any of the online vendors like SuperUnlockCodes.com to unlock it .