Account changes after death

I am in the middle of organizing affairs after my Fathers passing, both parents services were managed by my Father and no-ne else has the account information/logons.

I need to switch off his ID Mobile service but also keep and transfer my Mothers existing ID Mobile plan/number that she wants to keep into her own name/details (name, new bank account for payment, etc). I have the appropriate documentation.

I cannot log onto the online account as no-one has these details and apparently it is impossible to speak to an actual person at ID mobile.

Can someone please get hold of me to sort this.