I get it constantly.
"That's not a Manc accent."
"You don't sound like you're from here."
"You definitely aren't from here, where are you really from?"
I get it from so many people I meet and it gets so boring and small minded. Not everybody who is from Manchester or whichever region has a broad accent. I sound like I'm from the North rather than the South.
It's likely just people making conversation but surely it can't be really difficult to work out you don't automatically have a broad accent just because you're from that place?