Hello Senthilvelann
Maybe you know I'm an English learner from Japan. I too have troubles in understanding the constructs of "get O done".
Most grammar books say "get O done" and "have O done" are almost the same in the meaning and the difference is the level of formality.
[causative/benefit/intentional]
She had her hair cut yesterday / She got her hair cut yesterday.
[contra-causative/damage/unintentional]
I had my pocket picked in the crowd/ I got my pocket picked in the crowd.
[levels of formality]
You are required to have your car repaired / I'm gonna get my car repaired.
[imperative]
Get your license renewed / (?) Have your license renewed
However, some grammarians say that, in regards to the passive/damage usages, there are subtle differences in the subject's responsibility between the two expressions. For example,
Bailey discussed the difference taking sentences "He had his benefits cut off" and "He got his benefits cut off" as the samples. According to her, the former is to be used when "he" didn't know the cause why his benefits were cut off, and in the case "he" knew the cause the latter is a better expression.
paco