Firstly, thankyou to everyone who helped with my previous questions, we have sucessfully landed in Houston, complete with two dogs!

However, we are currently phone less, we brought my unlocked iPhone across with us with us with the intention of putting a U.S. pay as you go sim in it. We went to t mobile and he got ha a sim but it said phone didn't support it?! Any ideas why?! It's defisntly unlocked to all networks... Whats worse is my normal sim doesn't Appear to want to work and constantly says no service!

Was going to attempt to try and find an Apple Store tomorrow but any ideas would be greatly appreciated!

Hmmmm i brought an unlocked iPhone over and walked into AT&T and got a pre-pay sim and it works fine so far.

Maybe try another network?

Which model iPhone? At least some don't have the right frequency bands (UK and US use different radio frequencies, some frequencies are the same, but not all). It also, I hear, depends on which carrier's network you try to use it.

Search for other threads/ posts mentioning iPhones as this problem has been discussed several times before

It's an iPhone 5. I tried reading the others threads but got confused with all the technical stuff. Was hoping someone could dumb it down!

Will try another network tomorrow and see if that works!

Strange my unlocked 4s works on T-Mobile in the US and O2 in the UK.

Same here, no problem connecting to T-Mobile and EE on UK sim.

Look up the issues between CDMA and GSM phones. That may be it.

The iPhone 5 (unlike the 4 and 4s) is LTE / 4G compatible, but the world of LTE bands is far more complex than the world of GSM frequencies.

While there are 4 main GSM frequencies in the world, and most phones now days support all 4, there are something like 25 LTE "bands" (aka frequencies) that vary in acceptance around the world. The LTE bands used in the UK, and the iPhone built to support them, are not the same as the LTE bands used in the USA, and the iPhone built to support that.

iPhone 5 - Technical Specifications

All Differences Between iPhone 5 Models @ EveryiPhone.com

and for the 5S

Global LTE carrier support with the iPhone 5s and 5c for Verizon, AT&T, Sprint and T-Mobile

That said, you should be able to put a T-Mobile or AT&T SIM in your UK iPhone and get not only phone service but 3G internet speeds. There should be no problem with that.

I'd take it back to TMobile and say give me a SIM and let me try it out. Explain that is only LTE that doesn't work and voice and 3G data should be fine.

Good luck.

A "band" is a block of frequencies. Technically calling them "frequencies" is incorrect. ..... FM stations are broadcast on the "FM band", each FM station has an assigned "frequency" within the FM band.