It’s possible, but without knowing how familiar you are with networking, it’s difficult.
I’m assuming your Jellyfin server is on your home network. If this is the case, it might not be worth it because you have a data cap.
Your home’s isp probably designated your connection a dynamic IP (changes every time your modem is rebooted and also periodically). You should be able to reach Jellyfin through this IP right now if your router is forwarding http requests to your Jellyfin server. For example, if Jellyfin is watching port 8080 for http requests you would need to set your router to port forward all requests on 8080 to the Jellyfin host
Since you have a dynamic ip this would not be a “set it and forget it” solution. There are ways around this, you’d need to research buying a domain name from a registrar (I’ve used porkbun) and setting up a ddns client that updates your ip with the registrar when it changes. I haven’t been able to figure this out yet (I just tinker with computers I don’t know what I am doing. I also have capped internet so I’m not interested in hosting my Jellyfin outside my home).
Also, setting up https is a good idea and is easier if you have a domain ( but you can do it without, I hear.)
Good luck
Edit: the other suggestions about setting up your network as a vpn and connecting that way is probably much easier. I went the domain route for some other stuff I was doing.