Old mobile phone only shows emergency calls only

[ELS122]

I have many old phones that always show "emergency calls only", but most of them would start working again if I squeezed the phone around the cellular antenna area, so I'm assuming they just had failed solder joints.
but I'm trying to get an old Benefon phone working, and it shows 2 bars of signal, it occasionally shows "searching for networks", after a while it just goes back to "emergency calls only" or sometimes "no connection".
if I call, it just shows "call failed"

I can't find info on if these old phones just don't work on today's signal standards, so do they?

[ELS122]

Is it the GSM network I need to have for the phone? because I found a map of GSM coverage for my provider and it still is used according to that map.

[langwadt]

bad connection to the sim card?

[ELS122]

bad connection to the sim card?

I checked and moved the sim card around many times, it's ok, and I know the sim card works I've used it in other phones.
if I remove the sim card it just shows "insert sim card".

it's a Benfon TGP75EU, can't find a manual for this specific one but the TGP71EU says that it supports GSM900 and GSM1800, but not E-GSM... 
and the TGP65EU only supports GSM900

[Halcyon]

GSM-900 etc... are just the frequency bands that are supported by the handset. You also need to consider the type of network you're connecting to and whether your old phone supports them. A lot of those old phones were 2G only, which has already been phased out in many parts of the world. Next to go will be 3G, which in Australia already commenced in 2019, with a complete shutdown of 3G services due to happen in 2024.

Check to see what types of networks your carrier provides in your area.

[50ShadesOfDirt]

Ditto on a handful of old phones lying around in shoebox, including my beloved moto StarTac from many years ago (or thereabouts). 2G & 3G killed off in my area (ATT), and 4G LTE probably not far behind.

This thread made me think of building my own 2G "tower" (EnodeB), and sure enough, some folks have done such a thing, with not many parts or costs. It's a bit of a rabbit-hole (and I'm still slogging through it all), but basically a few folks and org's have put together SDR & such, rolling their own sim cards, to the point where two old phones can talk to each other, and can use the internet to talk to the rest of the world.

"If Police Departments can buy a stingray on government funding of a few 10's or 100's of thousands, we should be able to hack something together for a few hundreds" ... one of the hacker's wording.

OpenBTS.org ...

various Hackaday and github pages for same ...

Also found a company that sells "turnkey" solutions for a "testing" tower in a box (EnodeB, GnodeB flavors) ... one of the hacking pages listed it. But I hate paying for it if it can be hacked together ... and I love SDR projects.

Again, lots of reading ...