Well I didn't realise anyone under about 30 ever used a phone to call anyone, but there you go. I thought it was all rambling WhatsApp voice notes these days.
As it happens, I've just looked to change my SIM and I wanted to try the EE Network because they have the best coverage in the areas I go to (in reality, if you don't go anywhere particularly unpopulated or with inconvenient hills I think they're all much of a muchness). I found there was less choice of cheaper deals with EE or the secondary networks that use their coverage (although I need it to work in the Isle of Man, which is a particular difficulty as many don't include there in the roaming allowance) so it would probably be worth trying another network. You can check their coverage at:
https://www.ofcom.org.uk/mobile-coverage-checker
So providing that you're moving in mostly urban/suburban environments, just try a 30 day rolling SIM from anywhere in case the coverage isn't good where you are. I've swapped several times to look for better coverage, it's really easy to do. TBH I don't know why anyone has a full contract these days and PAYG seems fairly unnecessary unless you never use your phone as the cheapest SIM only deals start at under £2 per month.
Moneysaving Expert lets you search for all the deals, by allowance and what network is used. They all have unlimited calls and texts these days, because most people use hardly any, it's all about the data allowance, I don't understand why you're paying so much for so little to EE because you can get 50 Gb for well under a tenner, not that most people would need that amount unless they're literally watching videos 24/7 so maybe they do.
https://www.moneysavingexpert.com/cheap-mobile-finder/sim-only/
But if this is a sign that your DS is influenced by peer pressure and branding such that he wants things that are more expensive, this is a good lesson in 'expensive network is £15 pm, we can save £10 a month by getting exactly the same thing from Lebara/iD Mobile/Smarty. You can either have the expensive network or the cheaper one and £10 a month to spend on something else, which would you prefer'.