Simswop done,account NOT in arrears, yet service still suspended.......?

I recently, finally upgraded my contract after my phone was ****** a few months ago. Simswop was done, which does take time.. however, I can phone 111 from the phone, and receive calls, however, cannot make them. The account, I have confirmed is not in arrears, my last debit order even went off, and because i had no phone, I have accumulated airtime on my number as well. Each time you phone the call centre, each agent seem to have their own version as to what the problem may be.. from selecting a cell network, to the line still being blocked because the phone was ******... to the upgrade still pending? Seems rather that everybody seems to be grasping at straws instead, because clearly nobody seems to know why, or what the cause of the problem could be? I have spoken to probably 5 different call centre agents, of which one was kind enough to hang up whilst I was still holding.....