unhappy day

Today is weekend,I should rest and have a good time.but because of  a sudden overtime.This is not the most bad thing.When i go to the company,want to know how the problem happen.To want know how often the problem happen,and i ask the colleague who are working ,but she ignore what i ask,then I'm feel not comfortable.and ask again she say:"I don't know",and attitude is very bad.
   What was i do wrong,why.I overtime do work and never want to remuneration,but the result is cruel .My friend ,please tell me what i can do.