PAYG as a gift - adding credit question

[EAB]

I can't find the answer to these specific questions in the PAYG top up FAQ, so if a mod is reading they might be worth adding...

I am buying my mum a phone for Christmas, and want to set it all up for her. If I call 4444 to top up, will MY card always be registered on her phone? I don't want her to think she's paying for top ups when actually it is my card it's coming off.

In fact as a general question, when you top up for the first time with a card, is that card recorded so next time you just tell it how much you want to add and you don't need your card number again?

In summary, what is the best way to give her the phone with credit on but make it set up so she can add her own money as easily as possible?

Thanks in advance
Ed

[MI5 · Accepted solution]

You need a voucher for the first top up anyway so buy one from your local newsagent etc and apply to phone.
Your mother can then register her card for future top ups.

[Cleoriff]

To answer the other part of your question @EAB. Once you use a card to top up, the O2 system keeps that card info on file (as such)  So the next time you just enter limited details and key in the amount you want to top up. It is a very quick  process after the initial one