@Sunflowers2811
YANBU OP. This pisses me off too. it used to happen to me, but not so much now. DH has always got it a LOT though. So much so, that when we moved house (several years ago) and changed our service provider for our phone and internet, he got another mobile phone, and kept the number to himself, and also they never got our new home number.
THEN they started hounding him on fucking facebook! So he switched off 'chat' and so they'd post on his board; DAVE can you come in tomorrow morning on a 7 til 12?!' On his fucking facebook page. His manager is not even on his friends list; she got a colleague of his (who IS on it) to send him a pissing message. 
So he quickly deleted all 13 work colleagues he had on his facebook, blocked them, then deactivated his facebook. He told everyone he had cancelled it, kept it off for a week, then reactivated it, and changed his name on there (so say, if his name was Dave Dill, he changed it to DeDe Jones (Jones being his mother's maiden name.)
His boss keeps moaning that she cannot contact him when he's off as she has no phone number for him. He keeps saying he hasn't got one. No home number and no mobile number. She actually asked for MINE a few months ago. He told her I would go batshit if he gave my number away!
I don't know for sure, but I don't think it's LAW that an Employer has to have your phone number. I am pretty sure though, that they are breaking some kind of 'privacy' or 'right to quiet enjoyment' law by hounding someone on their bloody facebook page, asking them to come into work (on their day off!)
DH and I have suffered also in the past, by our Employers messaging/ringing us in the middle of a 10 to 14 day holiday-leave period, asking us to come into work. We have been abroad a few times, but some of the times we have been holidaying in the UK, and they seriously do not 'get' why we won't drop everything, (halfway into our 10 to 14 day holiday leave,) and leave our family holiday and come into work!
I was even messaged to come in, when we were in fucking Egypt a few summers ago, as it was the 8th of our 10 day holiday. I was asked 'is it possible for you to leave a day or 2 early....' Unbelievable!
Thing is, some of us love our family and friends, and the time we spend with them, a LOT more than we love work!
I work to live, I do not live to work!!!