Reddit is probably your best bet. You can post in your provider's sub and your local subs. You can always make an alt if you want more privacy. It's hard to give generalized advice. Also - local people in particular can be a great source of info.

They have me being billed for a landline.

If you live in the US or a place like it - you could say "I do not want a landline. Please give me a better deal." That's what I'd do. And if they refused - I'd politely ask to speak to their supervisor. But I'd still check reddit first.

Idk what American sales is like, but I'd at least try calling first. Worst case scenario, your billing stays the same.

If they insist that you should have a landline, just say no. You can just keep saying no calmly. Keep saying no until you get what you want.

Are you getting some form of DSL? If I remember correctly, you'd need a landline in order for the internet to work. Maybe that's why they're also billing you for a landline?

I'm unsure of any "legislation" or anything that you might be able to search around for to resolve the issue.

Every company can do different things, I don't think there are any "rules" for/against this. You might be able to talk your way out of it, but when I tried to talk one local utility out of paying for a landline that was part of the internet package they politely told me to fuck myself.

After the electric company decided to do internet stuff in competition with the phone company, the phone company's internet packages stopped having a landline bundled. So maybe you could harass customer service until they dropped the phone line charge.

Though I don't know if there's a requirement by certain companies organized in certain ways (like if the phone company is set up like a utility or something) that require it to have a means for 911 (or whatever your local equivalent is) emergency services to be able to ID your home's location.