Sister's phone on O2 now says invalid SIM

[HHGTTG]

My Sister does not use her Doro PhoneEasy very often but today she turned on the phone only to find 'Invalid SIM' displayed on the screen and hence cannot make any calls. She had plenty of balance but does this mean perhaps she has not used the phone often enough?

[HHGTTG]

Thanks but I thought that 1p mobile now require minimum of £10 every 90 days to maintain one's account so £40/year. I already have an unused smartphone with a 1p mobile SIM in it and so presume I can get the appropriate adapter to enable this to be used in my sister's Doro phone that only takes a standard size SIM?

Does unlocking her Doro phone, say online, from O2 cause her to lose her O2 balance?

[MI5]

@HHGTTG 

She will keep her balance on the O2 sim. Unlocking won't change that Guide: Unlocking an O2 phone to use a different SIM card 

[madasaf1sh]

@HHGTTG 

It gets worse with 1p mobile now as since Feb this year, if you dont have enough credit, they suspend your account, and then kill it off 10 days later

No longer recommendable in my view, if you want a calls only on o2 look at Silux Mobile https://siluxmobile.co.uk/product/promo-sim-o2-sim-only/ maybe worth asking them how to top up.. and what the rules are on the promo sim card.. 

1p Mobile new terms

[Enlli]

Your right with Ip. 

I paid for a year at the beginning of Feb at the old rate. Glad I did

[HHGTTG]

Hmmm, thanks but their website looks a bit amateurish but I have emailed them and asked how does one top up their Promo SIM. Perhaps it's just that and it is a promotional SIM just with a 6 month life to test the water, so to speak.

[Enlli]

Never had any problems with 1p. I use them as backup in my dual SIM phone.

I pay using a Debit Card