I've read an fml similar to this before! FYL OP!

Yeah, it sucks to get called in on a day off, that has happened to me before. If you get called in, (you have no choice but to go & can't say "sorry, can't do it") then technically it becomes your shift & yeah, you can get in trouble for being late. My work gives a 15 min grace period (from the time a shift would start) & if I show up 16 or more min late, I get a mark...3 marks=3 day suspension, 1 additional mark=termination of my job because they see you as "non compliant" &/or "unreliable" as well. I have a total of 1 mark this year for being 17 minutes late. Bosses can be jerks when calling you in on a day off.

I didn't mean to click the deserve button how does one unclick the button

Voicemails, buddy

I wouldn't sign the write-up slip and call HR or Union (If you have one). Anytime I get called in, i always specify that I might not making right when they need me so they don't expect me on time even though I usually am when I get called in. that way they aren't mad if i am late and really happy when I show up when they need.

bosses suck

I would take it up with HR in the presence of an attorney

Your direct boss that wrote you up is an ass. Go over him/her and appeal the hell out of it.

I'm pretty sure that's illegal...

I know the feeling. Only im on time and my managers are late :(