IPhone 4s 3G network is enabled but not working

Hey ya'll i'm having a problem with my 3G network on my 4S

My original contract phone was Blackberry 9900 and few days ago i sold that and bought myself the IPhone 4s, and i have ordered a new micro sim with the same contract plan that i had on my blackberry, and since i got my Iphone my 3G stopped working. The cellular data is on and everythings else is working perfect. The 3G icon is displayed at the top left but it won't let me access the internet or anything. I rang Three numerous time and did what they told me to do, reset setting, troubleshoot etc. I did all that and still not working

i would appreciate it if someone could help me with this!

Go to Apple

If the 3G icon is displayed, the phone is working properly. If you can't access the internet you need to speak to your provider for the settings. If they can't sort you out then return the phone, cancel the contract and start again, preferably with a shop with real people in it who can sort you out.