Little help needed please

[bottomsqueak]

I have a nokia 5210 which is an ex contract phone but fully unlocked. When i put any pay and go simcard in, it displays "sim card registration failed" Why would this happen and what can i do to correct it? I tried my friends vodafone simcard and it was fine. I have reset the phone to factory settings but im not sure what to try next. Any help would be greatly appreciated. :D

[Stu_Millard]

Sounds like it ain't actually unlocked......

[ditnuj]

The phone is unlocked. But the sim card is not valid. So, if the sim card was on a contract but that contract is now ended, then the sim doesn't work anymore. Only a sim card on pay as you go or a valid contract will work.

[scotsland]

if you need a new sim i can supply