Search Amazon or eBay for O2 classic pay as you go sim
There are 20p SIM's out there that can still be used and get the 3-2-1 tariff with traditional credit that remains on condition that you have at least one chargeable call every 6 months.
This is what the O2 web site currently says;
Classic Pay As You Go
With Classic Pay As You Go, you pay for what you use, as you go. The minimum top up requirement is £10.
If you don't top up, or add a Bolt On at least once in any six month period, your mobile will be disconnected and you'll lose any credit on your account. If you want to be reconnected you'll be given a new mobile number.
Please note, this tariff is no longer available to existing customers wishing to switch to the tariff. If you are not already on this tariff you will not be able to switch to it.
PAYG Terms & Conditions:
6. Tariffs no longer on sale (“Legacy Tariffs”)
6.1 If you’re on a Legacy Tariff that is no longer available to buy or switch to, these Tariff Terms also apply to you. Whilst the Legacy Tariffs are not in general available to buy or switch to, a small number of customers may acquire and activate a Legacy Tariff SIM via our indirect channels. These customers will remain on the tariff until further notice. If you switch away from a Legacy Tariff you will not be able to return to the tariff at a later date. Legacy Tariffs include, but are not limited to:
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