I've recently changed my SIM only contract to an upgrade with O2. Did this through talktalk. I got a PAC code which I sent to O2 and my number will be moved to new SIM on Wed 8th April. Do I now have to cancel my contract with talktalk or will this happen automatically when my number is moved?
TalkTalk will know that you've been issued with a PAC code and so long as that's used within it's 30 day validity then O2 will notify TalkTalk automatically of the number porting and at that moment your TalkTalk Mobile contract will cease and your final bill will be produced.
So, nothing more to do except enjoy your TalkTalk discounted O2 package.