andykeen said:

Pay monthly is just a contract phone mate it will be 12 or 18 months contract and you will have to pass a credit check, be over 18 and pay by direct debit on the same day every month.
Benefits are cheaper calls that PAYG more flexibility, no top ups etc etc but you need to look at your usage and get the right contract for you.
Hope that helps

andykeen said:

Doubtfull, that you can choose, it usually depends when you set up the contract. For 25 quid you should be able to get a pretty good deal. Check the papers for promotional deals, shop around the mobile shops to get the best deal. Once you are locked in to that 12 months you are stuck with it. there is a reason they give you a great phone for free remember!