I'm not teaching a class, here, bud. If you need me to tell you that running LineageOS isn't somehow a skill equivalent to walking into a store, then we have some serious cultural differences between the US and EU regarding average luddite phone ownership.
The stores don't charge for helping you, no. It's the same cost for service instore as out, at least in my experience. For all I know Tmobile started charging 'install fees' for putting sim cards in.
If I asked my mom for her SIM card, she'd ask for her purse so she could attempt to find a credit card that doesn't exist.
She has no idea how a phone works in any capacity. I'm not being insulting about it, I am informing you of blatant and honest truth.
My cousins, people my age are a hard maybe, I know two family members who went in-store recently. They treat their phones like cars. They use them and that's as deep as it goes.
Start by making some content for the systems you already fucking have. My ps5 gets closer to facebook marketplace every day.