I have an old Nokia 2190 & have wondered why some SIMs work fine (like most of my 'roaming SIMs') but others, such as my T-Mobile USA SIMs, my H2O SIM, and my Mobal SIM, do not. Also, the newer dual IMSI eKit UK/US SIMs do not work in this phone either. The phone is unlocked so that can't be the issue, can it? Do some old phones simply refuse to work with certain combinations of SIMs?