tonra34 Have you considered 1pMobile PAYG, operates on EE's network, or, Smarty's £5 Mini plan with unlimited minutes, operates on Three's network, for your mum? Depending how much she uses the phone you might find one of these better value.
1pMobile is working out a lot cheaper than giffgaff for my elderly relative. Only 1p per minute! You have to top up a minimum of £10 every 120 days to keep the SIM active but thats still only £30 per year/£2.50 per month. giffgaff PAYG is expensive at 15p per minute.
If you want a refer a friend code to get £5 free credit on 1pMobile let me know. Or, if you use Quidco or Topcashback they usually offer cashback for both 1pMobile and Smarty.
EDIT IMPORTANT! I've just read your other post. If your mum has a Doro 1360 then Smarty is no good for her as that phone is only 2g and as Smarty runs on Three's network it has to be 3g.
1pMobile would be fine as they support 2g and you already know it will work in her phone as it uses EE's network.