Interesting. I bought a Passport cheap last year to replace my old feature phone - works a treat, no problems with signal. I wonder if it's a US vs EU thing...?
cellular has bands, usually one carrier operate on handful different bands. Sometimes a phone only supports some of bands that don’t used in areas you live in.
When a phone nerds buy a phone they make sure which operator use which band or which bands are extension of which bands or which subtypes of a phone supports which bands before they proceed to buy one.
e.g. if a guy wants a phone that support Band 1, 3, 5, 7 and operator A use 2, 4 and 7 but only on rural, while operator B would use 3, 5, 9, 11 but 9 is basically 1, then he’d get a SIM from operator B.
Old Nokia had suffixes to commercial name like E71-1 for NA or E71-2 for EU and so on, as well as model number like RM-123 that each covers most bands in a region. Apple use different model numbers like A1234 for APAC, A1345 for Sprint US, A1243 for rest of US etc etc. On Samsung it’s N3546 for Korea and SM-i3456 or something like that, Sony/Sony Ericsson was XXnni for international and XXnna for CONUS at some point, sometimes completely different like “Xperia Something W12345”.
I can’t pull up BlackBerry scheme out of my memory but I think it was similar to Nokia.
You're commented prompted me to take out my Passport again, and we'll see if things have changed, thanks.