I've just gone to order a BT Mobile SIM only deal for my dad who doesn't need data and until Monday evening (21st November 2016), BT are offering their starter SIM at £5 per month which includes Unlimited calls and Unlimited texts and 500mb of data. The best bit is that going through Quidco, they're offering £49.50 cashback on all Sim Only deals plus the £30 Amazon Gift card BT are giving away.
In effect you will make a profit of £19.50 as worked out below:
Quidco cashback £49.50
Amazon Gift card £30
BT Mobile Sim annual cost £60
= £19.50 profit
This deal will not suit everyone so please hold the 'It is only 500mb of data' comments. This deal is ideal for my elderly father who does not use a smartphone and may help someone else. Good luck.