I have an iphone 5 with a sim card?

I've got an iphone 5 with a sim card does that mean that it is unlocked and ready to be used with any sevice provider and how would I find out if the phone is blacklisted?

Well then if that was the case then every phone in my country is unlocked.

A phone with a SIM card is a GSM phone. Doesn't mean it is unlocked.

Just a phone with a sim card slot doesn't say anything about phone's unlock status. The only way you could check is by putting a sim card on it. (If the phone is from any service provider try putting a different sim than its provider)

To check your iPhone is locked (or) unlocked do the following process:
Switch on your mobile phone with a sim card from a network other than the network you are currently with. If you are able to use the phone, you can be sure that your phone is not locked. If your phone displays an error message saying "Wrong sim" or "Incorrect sim" or "Emergency calls only", etc., then your phone is probably locked.

If your iPhone 5 is locked visit the site http://www.mobileunlocksolutions.com/apple-iphone-5/rs16wp9/ here they are providing the Remote Unlocking Service with easy step by step unlocking instructions. Using that you can unlock your phone easily. To find out, the phone is blacklisted (or) not contact the service center and check it.