Koala Maybe it's old age and experience, but if something appears to be pretty good, there usually has to be a catch. The 'mutual' friend was even bloody aware the phone had issues, so to me she isn't that good a friend.
My example is, many of us are marginalised into different groups by need. I fear the seller of the phone has little interest in whether she's a newly made single Mum. She just hoped she could get away with selling the phone.
I'm sure you've heard of scams, although I think this was a few years back, where people would try and flog electrical stuff on the street. Or back in my day you had the Sunday markets & car boots with Del Boys promising you the deal of the century. If you bought into it you would find you had bought something that didn't work, wasn't as specified and quite often was a hazard. A bit like the same markets / car boots that would sell knock off designer goods.
I remember there being a big thing at work when I was younger as i had gone to a high end shop and bought an actual Louis Vuitton bag. There was a woman at work who lorded it about like she was a fashion princess. She was telling others she had a genuine LV bag, Gucci bags, you name it she had it. I bought mine in and said nope, this is a genuine one. (Only because the girl was so far up her own arse and her designer stuff was far from designer!)
I remember there being an argument that in fact it was my bag that was the fake, she bought nothing but the best from insiders in the business. So I went as far as bringing in the receipt, the cloth bag it came in and even the LV shopping bag.
I didn't dress up to work as if I was on a catwalk, so the lads were inclined to suck up to her. It went to show how daft some people can be. Not related to this post, but an example of when fake stuff was peddled quite a bit. The imitation was no where near.
I think those that got suckered into buying phones off people in the street or car park, which obviously screams legitimate trader, they ended up being scammed.
So such an occurrence isn't repeated, please put the SIM card in, go to the text to try the keyboard as its a big standard keyboard for all the apps. The same with making a phone call, go into the phone section and test it out, can you dial the number you want.
As I've said if the OP has no luck, with a refund as a RAK, I have a 4S I think it is that I haven't used since my upgrade. I'll find it out & check it works if it's the same carrier as she uses. I don't believe unlocking phones is a good idea so this is specific to a certain network. We have spares, I'm due an upgrade on this so won't need my old one gathering dust. Anything to help a person in need.
But let this please be a lesson, I think if you fell on hard times, you're liable to sell your granny for a few quid if it takes you out of poverty. Not literally of course but I'm sure you understand the sentiment.