I'm sorry that you're having issues making calls. I want to look into this on my side. So I can do this for you, I've sent you a PM detailing the next steps. You can view this by clicking the purple envelope in the top right.
Mat After my initial complaint it got worse, from not being able to make out going call, I lost the signal altogether. I put a friends sim in my phone, and it worked fine, so I know the phone is OK and the sim is defective. I managed to borrow a friends phone and call back to Virgin UK. They reset my setting and the signal came back after 8 hrs. But I still can't make outgoing calls I am traveling in Asia so was very frustrated.