This felt uncomfortable, assalamu alaykum

Assalamu alaykum - A friend asked me to help with her cousin’s wedding a few months ago. She’s very close to her cousin, so she was helping with the planning and invited me to pitch in. About a week before the wedding I met the groom and his brothers while we were preparing things. We were chatting that evening and one of the groom’s brothers asked if I was single; I said yes and he just said “oh okay.” On the wedding night I saw him again. I greeted him and walked past, and he started talking about how well we did with the setup and asked about my job. I answered so it wouldn’t be awkward. Then he asked for my number. I said, “Don’t you have a wife?” He said yes, but that he didn’t mind having female friends. I politely told him I don’t give my number to married men, and he said he respected that. About a month later I got a call from an unknown number. I picked up thinking it was an appointment reminder, but it was him. He said, “Hey, remember me?” I asked who it was and he told me someone gave him my number and that he wanted to get to know me, that I’d been on his mind since we met and I should give him a chance. I told him respectfully that I would never break up a family and that his wife loves him, and asked him not to call anymore. He kept messaging and won’t accept no for an answer. I’ve asked repeatedly who gave him my number and he refuses to say. I asked my friend who invited me if she gave it out and she swore she didn’t. I’m not sure what to do next. I’d appreciate any advice on how to handle this while keeping things respectful and within Islamic boundaries. JazākAllāhu khayr.