AITA for my leaving my job?

So my boyfriend is calling me an asshole for leaving the job he helped me get.

He used to work there for 6 years. It was good for him I guess lol. He’s close with the manager and even as a teenager, used to come here for community service. He got me this job in December, where the duties were front desk basically checking people in and giving them information. During my interview, I was told this was not a position that has promotions. After a month of working there, I realized im basically just a security guard getting paid less than the actual security there($15 versus $21), where I have to stand up all day watching people and making sure nothing is taken or touched (I work at a museum) and was barely at the front anymore as the manager is always up there. Im a server and have another job so im always on my feet and only took this job so I can rest them, especially when there’s some days where I work both. A week ago, the manager informed us we’ll be taking on another role as after school education associates, staying longer hours, to help with the children that come here for community service hours.

I told my boyfriend I was leaving because there’s no way in hell am I doing the job of 3 people for the same pay. I already let being a security guard without any training or anything slide, I’m not about to agree to this. He says im being an asshole, they’re short staffed and need more ppl since 2 others in my position are leaving, not appreciating that he got me an opportunity that I can move up in, when there’s absolutely no moving up which he doesn’t understand because when he worked there, he worked in the office as a curator so he really only had one job and opportunities to go up.

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