Cheapest Sim For Occasional Use

[Galaxy1965]

I am giving my mum my old iPhone 5c mobile for emergencies etc and I don't want to fork out money each month for a service she won't use. She will only use it for the occasional text or call.
What is the best / cheapest sim she can use on an existing, modern, unlocked phone on PAYG that does not need to be topped-up each month ? Thanks in advance.

[Buenchico]

Asda will sell you a PAYG SIM for 50p in store or you can order one for free online. While most Asda Mobile users probably buy monthly 'bundles', there's no need to. You can simply put some credit (which doesn't expire) on the phone and use it when you want to . The only thing you need to remember is that the account will be closed (and all credit lost) if you don't make a single chargeable call in 180 days.

Asda Mobile uses the EE network, so there's good coverage, with calls charged at just 8p per minute (instead of the 30p per minute that you'd pay if you went direct to EE). Texts are just 4p each.

https://mobile.asda.com/

[queen 1954]

I use Three 321 sim,the credit dosnt expire and its very cheap at 2p a text and 3p a minute for calls.I probably top up ten pound approx every 3 months and you can get a free sim from their website.

[Old_Geezer]

It's not the topping up that's an isse so much, it's ensuring it's used regularly enough that the number isn't cancelled and removed from the database.

[ummmm]

I'm on GiffGaff. Although the bundles run out the credit doesn't.