Oh Lintu, I totally hear you. It's annoying, but at least it's just a conference call and you don't have to go into the office or anything. It's tough to maintain those boundaries. It really is.
FWIW, I just had a major disagreement with this project manager on Friday. I was supposed to be on vacation next week, but now I'm not. Someone decided that Tuesday would be a great day to have a kickoff meeting with all the team members from both sides... in Ann Arbor. So we leave on Monday and get back late Tuesday night.
So I point out that we don't really have time to create a bunch of mockups and design for them for this Tuesday meeting and honest to god, he says, "well, you can just do it over the weekend. Easy. Do it on the weekend and on the plane Monday, and we'll show them stuff on Tuesday. I told them we would have some mockups."
Um, no. I postponed my vacation because of these projects, and I'm not working this weekend. Sorry. When I pointed out that his request was unreasonable, he countered with "well, I'm going to be working this weekend."

I didn't back down. I do work some weekends when it is necessary, like when a project is launching and we are in final QA and bug fixing stage, but before a kickoff meeting, during a holiday week, when no one from either side really wanted to have until the following week? I don't think so. That is completely unreasonable, especially when you promise a client that I'm essentially going to be working all weekend without asking me.