Globalstar Ericsson R290

Hi I hope someone can help with my problem - yeh I know the problem is GLOBALSTAR hahaha
Anyway I am not talking about Satellite reception
I have not used the R290 for about 12 months. Turned it on last week in Cell mode (GSM) will not work - all indicators on the screen tell me its ok but will not send or recieve calls

I put the SIM card from my Telstra phone into the R290 = all ok works fine

I put the SIM from Globalstar into my Telstra phone = all works OK

So WHAT GIVES ???? HELP

I spoke to Pivotel who suggested I get a new SIM card - I have done that with one of their agents - still no go - Pivotel are sending me another card to try

Could itbe something to do with 2G or 3G or GSM900 ??