HTC 8s won't recognize SIM card

[WPCentral Question]

I recently had to reset my HTC 8s to factory settings and after that it came up with the message 'SIM ERROR'. I figured it was the SIM which was broken so I ordered a new SIM from my service provided (GiffGaff). It's just arrived but my phone is still coming up with the same message. Is my phone's SIM card completely broken and is there anything else I can do? Thanks.

 

[Laura Knotek]

Is the device branded to your carrier?

If not, is it unlocked?

 

[alex atherton]

Original poster here, I'm not entirely sure but I think it was unlocked when I bought it. Is there a way to check?