Close mobile account from overseas

[#1]

How can my family members close her mobile account now that she overseas. When she follows the website instructions it says her account will only be closed once she gives her STAC number to her new supplier. She will not be having a new supplier as she is overseas. She cannot call Plusnet from overseas as she don’t wish to pay an enormous charge.

Thanks.

[#2]

If your family member still has a plusnet contract with inclusive minutes can she use those minutes to phone Plusnet without running up a bill?