And here's why:
The idea is that teachers teach each other and switch every month.
If you join for one lesson:
a) this might be the first lesson for this particular teacher, and, we all know, first lessons can be overwhelming,
b) next month - next teacher,
с) you might be this teacher yourself :)
This makes the concept of a trial period absolutely impossible.
On top of that, you're not paying for each lesson, but for the programme. We have invited guest speakers, and provide a complex service: group lessons, webinars, SIGs and a lot of extra stuff. The programme for our General English track is for 3 years, so joining for 3 months is a trial period in a way.
We aim to keep the minimal price so that the majority of teachers from different places all over the world could afford it. We can't and won't cut down on the quality of our product, but we can reduce admin work, that's why we're asking you to pay for a minimum of 3 months.