Registering new pay-as-you-go SIM card

[Firefox1701]

I've just ordered a new pay-as-you-go SIM card for a phone that was given to me by my son.    I've inserted the card into the phone and it appears to work perfectly,  inasmuch as the phone can receive calls.    As it stands,  that's all I need it to do;   so my first question is,  if that is all I need it to do  -  if I don't need to use it to make outgoing calls  -  do I still need to register it,  and if so,  why?

My second question is,  what's the actual benefit of registering it?    If I do decide to use it for outgoing calls at any point,  can I not just call 150 from the phone and top it up as need be?

[XRaySpeX · Accepted solution]

@Firefox1701 : 

1. You don't need to register your PAYG SIM to MyEE online. You can still use it for all its functions by using the far easier PAYG Text Service to buy packs & add-on and monitor it. Even if you did want to make outgoing calls, all you need do is top-up.
2. There is no real benefit to be had from registering it. It just lets you manage everything in 1 place.
3. You've no need to call CS. You can just Fast Top Up online with a UK bank card. You don't need to login or register anything. All you need is your mobile no. & it doesn't remember your card details. 

[MrGeorge]

I’d say registering is important for two reasons. One is for security. Having your account secured with a password is important if you use your phone for 2FA ie when you get a pin sent by text. Another reason is for sim replacement in case of lost device.