I have an T-Mobile HTC MyTouch. I recently unlocked my Mytouch. I didn't get a signal although I did get a, "phone unlock successfully." notification. However, I get no signal and when I go into settings to check network connectivity. I have an "Invalid SIM," message. I want to use the phone with multiple carriers, as well as, use it in other countries I frequent through out the year. I went to the store of a local carrier that I use and he said that the IDN is different and the SIM will not work in the phone I had. I was wondering if this is the case. My understanding is that all SIM cards are the same. The FF for both SIMs is the same. Is it a matter of changing a setting in my phone or is the agent of the local carrier correct?