prehistoric phone... what band it works on??

[Thanh]

Hello
I am owner of a really old Ericsson phone. It is the model "NH 237", Type "1941 C" and the only thing i know of it is, that it is definitely analogue.
It has no sim card, instead a small PCB with electronic components, which can be taken out and replaced. This phone, when i got it, hasn't been used for several years, yet still could be charged (no charger though... connected 6v power supply direct to the battery) and then works. I get network (showing only "TH" on the display) and can even make calls! But:
1) i can call only to land lines in Bangkok, not mobiles and no ther cities
2) even digital landline phones (ISDN) don't show the number
3) calls get disconnected after a few seconds
4) after disconnection, phone loses Network and has to be restarted.
Now, i guess that is because this phone is not registered anymore, or has at least not been paid for a few years. I don't mind that, i won't use it for other purpose than collectors item. But, i would like to know:
Which band does it work on?? We have in Thailand still a variety of different analogue cellular networks in service, specially in greater Bangkok, where there's 900 MHz AIS (cellular 900), D-Tac's (former WORLDPHONE) both 800 and "new800", CAT's 470 (?) and TOT's service, which i don't know the frequency.
I want to know what network this phone model uses... I can't asdk at the providers, they might make me responsible for unpaid bills over several years. In fact, i got this phone by sorting trash from an old office which had to be cleared when my company moved in.
Anyone can help me out? Thanks a lot in advance.....
your Thanh

[gsmdave]

Sounds like a load of old junk throw it away and get a new Nokia