How to find out my network carrier?

I have an iPhone 4 locked to a Swiss network. I want to find out which network it is locked to as the phone has not been activated through sim yet although it has been hactivated (through jailbreak). Would I have to buy a bunch of different sim cards from Switzerland to see which one works? Is there any paid service I can use to find out my carrier?

Try hitting it with the heaviest hammer that you have got access to! N. B. SAFETY - Mind your Fingers & Thumbs!