Hi @Skelly thanks for your post although I'm sorry to hear of your concerns raised.
You will not need a stac code to cancel the contract, as we can book a disconnection as per the 30 days notice period. The STAC allows you to cancel your mobile number with your previous supplier when you change networks, but you will also be able to book the disconnection without one. The STAC code will be given to your new provider and this would activate the cancellation.
As you don't have a new provider in place (or at least to take over the number), having the STAC won't ever action the cancellation in this case as you're not porting the number over.
I can however, offer to help you with the cancellation if you wish - please reply if you'd like me to get this sorted for you and I'll Private Message you if so. If you'd prefer to resolve this over the phone, please call us on 0345 600 0789.