課金不可（日本からは勿論、現地でも）、そもそも期限切れ

www.three.co.uk
Pay As You Go.
Topping-up.

There are a number of ways to keep yourself or a friend topped-up. Choose your preferred option below to top-up your phone, tablet, Mobile Wi-Fi or dongle.
登録すればオンラインでの課金も可能ですが、一般的にRegisterは現地でないとできません（普通はそこまで余裕がないので、済ませてはいませんよね？）。通話不可のプランでも電話番号が与えられ、その番号で登録されるからです。

さらに、
We only accept cards that are registered to a UK address.
なので、日本人旅行者はほぼ無理・・・。

Three's Terms and Conditions
Pay As You Go Terms & Conditions
ここから先はPDF
Using Three Services
By inserting your SIM you are expressly requesting that Three provide you with our Services on these terms.
If you wish to use Three Services, you need to top-up your account by purchasing and activating Pay As You Go Vouchers. All Pay As You Go Vouchers and Add-ons must be activated within 90 days of purchase. Additionally, some Pay As You Go Vouchers and Add-ons expire within a certain period after activation, for example, 30 days. Validity and expiry periods (if applicable) for each type of Pay As You Go Voucher and Add-on can be found in our Pay As You Go Price Guide and other customer documentation.
最大90日で昨年末からはすでに六ヶ月経過しているので、潔く諦めましょう。

香港の3なんて屍SIMが山のようにあります・・・。ダミーSIMくらいしか使い道はないでしょう。