Debt collectors emailing me over charges I never used??

Hi there,

I stayed in the states for 3 months back in the summer of 2022 and as a perk of the accommodation I was in, they had a deal with AT&T. I signed up for it but they never asked for card details or a contract to be signed. A sim was meant to be sent to the accommodation I stayed at but it never came. I decided to go with mint mobile as it was cheaper and a better deal. I went into the physical AT&T store to cancel anything just in case and let them know I never received the sim. The store clerk said as long as I never activate the sim/didn’t receive it, I am fine. So I took his word for it and didn’t think of it since. I’m now receiving emails of bills owed of $149.72 and a debt collect, true accord has emailed me as well.

I’m freaking out because I’m now home in Ireland and although I had a “J1 Summer”, I have an American passport as I was born in the states. What the heck do I do? I’m not paying money for a service I never received or used, but I’m also scared this will affect me if I ever decide to live in the states. Please help!!