It is the responsibility of the passenger to always make sure that the names , details are correct. How you can miss such an error as the name is incorrect? Ok, so equally to blame is the travel agent who couldnt’ read english properly in the first place. But as the error is with the travel agent, and not with SQ, you should take this matter up with them.
SQ can only adhere boarding to what is on the reservation. If it was an error and of which it was spotted in time, then the ticket must be reissued by the travel agent. There would not be any additional charge because it was an error made by the travel agent and not by you. SQ cannot just change the booking even at the airport, because they did not issue the ticket.
You would unfortunately have to claim this against the travel agent.