The service code that used to work (I'm not sure if it still does) to turn off call barring was ##330*[pin code]# if you know your pin.
Try switching off and rebooting your mobile to renew its registration on the TalkTalk mobile network.
If call barring is still active then call the mobile team on 0345 172 0044 free from a TalkTalk service landline. Advisors are available 8am – 8pm 7 days a week so request the bar to be removed. Have your account details to hand when you call.