Uninvited visitors

My BIGGEST pet peeve is the people who show up at my house & do not call first.

I have some physical problems that require me to rest quite often & I am also plagued with migraines.
All of my friends know this and most call before a visit, just to make sure I will be up and able to sit and visit with them. But, there are a few people who think that calling does not apply to them.
They stop by because they are bored.....BORED, like I am willing to take them away from their boredom after knocking long enough to wake me.

I have repeatedly asked them to call first, but it just doesn't sink in. They think about visiting me while they are driving around.
If I didn't really love these people, I would offend the heck out of them and ask them to never come back.
I have found a temporary reprieve by posting a large sign on my door that states whether I have a migraine or am sleeping...and to NOT KNOCK under any circumstance!

I just wish some people would look beyond themselves and realize that some people have special needs...and would be a bit more considerate of their requests.