I ordered a SIM in early October. On 3 October I sent an email to Customer Services to ask for clarification about PAC. I received an auto-acknowledgement saying I'd hear from someone within 24 hours. When the 6th of October came and went without any contact from Plusnet I decided to cancel the "contract" that had not been set-up yet. I got into a protracted email conversation with Customer Services which ended with them saying that I had failed to provide the correct information 3 times. I then filled in a cancellation form and sent it to Customer Services on the 21st of November. Today, the 4th of January, I was appalled to receive a Mobile Bill on the account that should have been cancelled long, long ago.
PS I stayed with my old provider and have never used the Plusnet mobile number/SIM. I have copies of the completed cancellation form and the full email exchange for the SIM Incident.