Or you can try to do what i did. However this was a screw up on my last mobile phone provider and currently I am not so sure if I have been blacklisted or not (I hope not)
For about 3 months, I did not pay my bill. At 2 months, they put call restrictions on my phone. At 3 months, I can not longer get incoming calls. A 1 month later, they handed it over to debt collection agancy. About 3 weeks later, I call up the mobile phone conpany (not the debt collecton agency) with the sob story saying that I was house sitting and I only got back to my place too day. At this stage, it was 2 days after they canceled the phone contract. You pay the phone company what you owe them. You do this one a week end where they can not reactivate your phone.
Wait about 2 weeks, you will get a huge bill in the post saying that you have cancelled your phone contact. Call up the phone company and tell them that you did not authorised your phone to be cancelled. Again do this one a week end.
Wait about another 2 week later, you will get a credit note cancelling the huge bill that you recieved 2 weeks before hand.