You are hired on a low probation rate that is supposed to run two months. It is extended, repeatedly, so the cheap rate becomes your actual salary for months. Extending probation beyond the legal limit — and paying below the required proportion of the agreed salary — is not permitted.
Get the probation length and rate written into the contract with a hard end date. Ask what the full rate is and when it starts.
One person's account naming a Chengdu recruiter, describing six teachers they knew. We reproduce it as written and have not independently verified it.