Can anyone help me with a broadband question pls?

[OswaldOwl]

I know this is probably really basic, but I am stuck.

I live in a rented flat. I currently use the internet on my phone, but I am looking into getting Broadband now. There is a phone socket in the flat but nothing plugged into it.

I looked up some deals online, looks like it's cheaper to get a deal with a phone line than internet only. I began to sign up, thinking it would be straightforward, then the website says: "If you're having a new line installed, we'll book a time for an engineer to call".

AM I having a new line installed? I don't want to get a second phone socket installed, the landlord wouldn't be thrilled either I'm sure.
The existing socket has got the BT logo on it, but I don't want to go with BT, they're really expensive. I don't know what the current phone number is. I have emailed the letting agent to ask but they haven't replied to me, guessing they don't know either. This is a rental property in a student area with a high turnover, perhaps somebody has changed the number or supplier since BT put the socket in?

In short, what I want is to get a broadband-and-phone-line deal, using the existing socket, with a non-BT supplier, bearing in mind I don't know the current phone number or supplier. Sorry to be so feeble but how do I go about getting this?!

Thanks in advance for any pointers!

All phone lines are BT.

You just sign up with the provider you want and then plug it in. It’s really easy.

Okay thanks @SheABitSpicyToday. So if I get a broadband-and-phoneline deal, they're not going to send over an engineer to put in another phoneline?

No

For example sky, they will send you a box with everything you need in it and you literally just plug it in. And engineer can remotely turn the lines on, sky did our last week.

To get your landline number - buy a cheap telephone, plug it into your socket, ring your mobile - the number should appear.

..... if it's live!