It's the future. It's been the future for a while. Long waiting lists got longer, and the NHS was increasingly privatised, until it got replaced entirely, by MedPatch.
MedPatch, as you might expect given recent trends in technology themes, is a combination phone app and AI (which happens to be voiced by Meera Syal who has obviously been busy recently). It's been built on decades of patient data (which you might be sharing with other companies right this minute), as well as mirroring the skills of surgeons who use assistive robots. (Though it's worth noting that movement is easy - it's recognising the bits you need to cut that is hard). There's also a slightly hand-wavey "scan" in there that allows picking up symptoms somehow.
This has lead to a reduction in the need for trained medical professionals, such as Jenna, a former doctor, who has spent a very long time unemployed, but has finally got a position in a call centre for MedPatch. That took a certain amount of lying, as MedPatch doesn't like hiring medical professionals. They're very bad at trusting the AI. (Personal bias warning - as someone who has had a bit of experience on the fringes of AI, all of my switches are manual. I don't trust it enough to turn on lights, I'm definitely not letting it get its hands on my organs.)
Unfortunately, having got herself into the system, Jenna can't turn off her bedside manner, and so the plot begins when someone doesn't approve of her questioning. (This is honestly the least believable aspect of the plot in my mind - anyone who works in a professional field knows the fun of mates who always want a quick consult. We'd love access to our own personal GP.)
The rest of the tale is a thriller in the man vs machine mould, looking at the need or otherwise to "take down the system". The problem with that, as always, is that if the system were perfect, it wouldn't need taking down.
People are fallible - the play recognises this. It's why we have an inbuilt checking system - you ask your mate for a second opinion. Machines trained to replicate people will likely also be fallible. The old problem of garbage in, garbage out strikes again. So you can probably take a decent guess about where the play ends up. Still, it's a reasonable whistle-stop tour of the idea of AI in healthcare.