Yes, there seems to be two ways to keep the sim live depending on the provider. One is to top up a certain amount on a regular basis which is pointless for an emergency phone. The other is to make a chargeable call/text every so often which is fine. I think what I was hoping to find was what I now know is called Classic PAYG. I don't want to have to give banking or card details to yet another company.

From what I have read, most companies seem to have ditched their "classic" payg deals in favour of you having to pay for an upfront bundle of texts/calls/data each month. If there are basic pay sim's out there, the companies aren't in a hurry to tell you they are available, hoping instead to get you hooked into a monthly bundle.

Further to above, I have found a site suggesting GiffGaff and Asda both provide a traditional payg, you just have to pay a bit more for usage. I will investigate.

I use both GiffGaff and ASDA mobile - the former as a 'backup PAYG' because the per minute cost is now much, much higher (25p I think) than when I first went with them 12 years ago, plus they charge to pick up voicemail (a one off charge of 8p per call I think).

What they ARE good at is wanting an occasional month's full-on calls/web/text package at a reasonable cost, then back to PAYG with no penalty - e.g. a long trip on unfamiliar roads, a fortnight's holiday's etc, when you need full satnav, make calls to book things, browse the web, etc. Note that I think they only accept 3G, possibly 4G phones or better, so no good for people who want to transfer an older phone to them.

ASDA mobile, on the other hand, still provide a 2G service as well as 4G+ (they've just switched off their 3G one, so any 3G phone [older smart phones] can now only take advantage of their 2G service). They also have much lower rates for calls than GiffGaff on PAYG, and allow the picking up of voicemail free of charge at the moment.

I use ASDA mobile for a 'normal' PAYG service, when I'm out in my car or on my bicycle (and don't need a full satnav function - my old Nokia 620's built in one will just use GPS with no traffic, so essentially an active map), handy in an emergency or just to tell someone I'll be late as I'm stuck in traffic.

Both providers have a min use of one paid-for call or text per 180 days in order to keep the service/phone number going. For GiffGaff, that also includes taking out a 1-month only contract (i.e. it resets that period back to zero). They both may also say that adding a top up payment also resets to day zero.

Both seem fine to use. I also believe both a 'secondary tier' services, i.e. their users get lower priority than the main provider of the actual mobile services if something technical goes awry.

Best to check the Ts & Cs - I just put down what I can remember off the top of my head.

Just get any old PAYG SIM and don't put any credit on it. It will still be able to make 999 calls

Pay-as-you-go SIM that doesn't expire?

3 PAYG allowance is there for as long as you need it.

You need to make the odd call to keep the phone number alive on all networks and the requirement varies from company to company some every 2 months some much longer.

One point to bear in mind is that some providers used to offer this generous set of terms, but no longer do.

My very, very old Nokia 3410 from 2003 was originally on (and locked to) Virgin mobile, but at the time, I was ok to stay with them even after a good few years, because they charged on 15p/min, nothing to pick up voicemail and quite cheap for the few texts I needed to send. There was no minimum time in between paid-for calls and the top-ups stayed on until you used them.

A few years ago, that all changed, significantly increasing the per minute costs, no free voicemail pickup, etc, etc, plus, despite them saying it was fine for an old 2G phone like mine, coverage was terrible - calls often dropped out.

That's why I changed to ASDA (and not just had one provider in GiffGaff, given their per minute PAYG rates went up by 100% to 25p/min), which at the time charged a great price of 4p per minute/text/MB data. Now higher, but still reasonable, roughly what I used to pay with Virgin.

Providers have a very sneaky 'get out', by which they can change the 'contract' for PAYG, but have to offer you a 'get out' by saying you are 'free to leave', and give you advanced warning of the change. Not such of an issue if it happens infrequently and there's a lot of competition at good prices, but that's no longer the case.

That's why I have two service providers rather than one, and why I bought a dual sim smart phone back in 2020, so when my older phones break (not economic to fix) or the older 2/3G service is switched off, I can use the newer phone for both.

The only reason I use the middle older phone (Nokia 620) is because it's small and has good battery life when in 'dumb phone' usage, so is handy for cycling and can easily fit in any pocket when I'm out and about.