I have received a letter from Immigration dept. The address and their refrence are correct. But inside the letter, they did not addressed me but someone, as Dear Ms.SomeoneElse, And the funny thing here is they changed the gender too.
What shall I do now with that letter? Any legal claim?
Legal claim for what? I'd be doing the 'good citizen thing' and either sending it back to Immigration (with or without a sarcastic comment attached) or taking it back in person and pointing out their error, and trying to work out if any of it is actually meant for you.