This is a scam, they will take your money - Anonymous employee 51Talk Employee Review

This is a scam, they purposely have it set up so that you won't be able to enter classes and then "penalize" you by taking money out of your account. Do not give them your bank information. If they were an American company, they would have been investigated and put in prison for all sorts of white collar crimes. All they have to do is put up fake "good reviews" and make it so that a few people have some success on it so that most people will fall right into this trap.