You will need the password off your dad, VM will charge £20 to change the contract to your name, alternatively keep the same account & change the direct debit to you & your moms bank account, needs account password for this. If you are still in contact with your dad then he would do surely this for you.
Beware of canceling an account, you can't order a new account from the same address with the old account still active & you will be cut off until the new account activates. This is happening to me right now as my daughter has moved away & it was her account, I tried to get it as a new account to get the special discounts, they signed me up yesterday with new account to start with engineer visit Feb 13th, this morning no TV no B/band until Feb 13th, had to spend all morning on the phone to get it back on, only alternative is to chang account name to mine £20 fee, can't now get new subscriber deals
Aso it appears that if you cancel then when it activates you have to wait a month to reorder