What should I do if there is a mistake on my multiple re-entry permit in Thailand?

Asking for a daughter’s friend. She is on extension of stay for education valid until 28/10/2019. In February they got a multiple reentry permit. At immigration they made a mistake and wrote 28/08/2019 instead of 28/10/2019. They did not realize at the time, they noticed now, and need to go and have this corrected. They are in Bangkok. Can you please help and let me know where exactly they have to go. Thanks very much.