Work issue,AITAH

I work in a company and if we take and book appointments after hours we get a commission per appt. A previous employee had the calls together with his girlfriend. But all the appts went onto her check, so by paper trail, he never took any of the calls. The girlfriend got fired. He went on medical leave. While they were gone, I stepped up into the company, took over both their positions and the overnight calls. I've basically been working 13 hour days 7 days a week since May! Upon him coming back I was assured I would not lose the overnight calls. Within about 6 weeks of him being back I was approached and asked if I would share the calls. I said sure. He could have Mon-Friday, I would keep Saturday and Sundays (prime days) then I got approached again, could I share Saturdays and Sunday. I said no. That instead, he could have Saturday from 4pm on and share Sunday. (Not theres a other branch of an issue here, he was given these days.. the Mon thru Friday and the Sat after 4 and sharing Sunday, BUT.. he ends up not taking the calls. All week long the calls end up coming to me, Saturday comes and at 4pm the calls are still coming to me, sunday comes, his number is put in for the calls, but they all go into the abandoned and come into my email, so I call them and get the calls) Now for the last few weeks I've been approached over and over again by him.. every week he comes to me on Friday and says "has anyone talked to you about the calls?" because he's now wanting Saturdays, for me to take mon-friday and sunday and he take Saturdays. (Saturday is a prime prime day, guaranteed 30 calls, the other days are hit and miss) or for us to switch off each week, he take one full week, I take one full week. My issue is... I don't understand why this keeps being an issue. I don't understand why each week he wants to change it. (I know its not management, I know its HIM going to management and bugging them about it, management doesn't care who takes the calls as long as the calls are answered) But each week... its "did "manager name" talk to you about the calls?" and its always on Friday... right before Saturday. So we get to last Monday. And as I'm leaving the office, he asks me "can you take the calls tonight?" I'm like, sure. Then all week long the calls stayed on me. We then get to this morning... SATURDAY MORNING day of.. and in the group texts hes like " whats the plan for the calls this weekend?" and I'm like "I don't know what you mean". and he says a manager was supposed to talk to me, that he was going to take Saturday (today) which is WHY he left the calls on me all week, and I would take Sunday because he couldn't take Sunday ( he says its for Church.. I KNOW ITS FOR SUPERBOWL!) and then manager in the chat basically stated what I did.... that they don't care who takes the calls, as long as the calls are taken and that they need US to communicate and work it out ourselves. I finally had enough and stated: I just don't understand why this keeps being an issue? Its very simple. YOU have Mon-Friday, and Sunday (6 days) I have Saturday, that's 1 Day. If there's a night or day that you can't take the calls, I'm more than willing to step up and fill in, but I don't see where that should negate me keeping my Saturday. If I had to not take my Saturday and ask you to take the calls, I would not assume that it means I get all week and Sunday.. UNLESS we ask that of each other a week ahead.. but this is now day of..... and your telling me you left the calls on me all week in exchange, ...well, no one asked me to do that... no one asked me to take Sunday,... what I'm figuring out is....he's asking the managers to talk to me, but they are as tired of it as I am, each week he wants to buy everyone about it. So my final is as I said... in the group chat even with the managers, I stated: I just don't understand why this keeps even being an issue. You have Mon-Friday and Sunday. I have Saturday. And I don't really don't think, you not being able to take one of your days should interfere with me taking my day and vice versa. Unless requested well in advance and not day of. So AITHA? basically I went from being assure to not having to even share the calls, to sharing them, to sharing them more and now each week, its a problem but from his end.